JNI: Handle the case where an object's native pointer is NULL.

If Java code creates e.g. a Document object and later calls
Document.destroy() and then keeps using the Document object
the library would end up crashing because the native pointer
was null. This case rather special case is now handled.

1 files changed, 307 insertions, 246 deletions

diff --git a/platform/java/mupdf_native.c b/platform/java/mupdf_native.c
index f712f972..823846bc 100644
--- a/platform/java/mupdf_native.c
+++ b/platform/java/mupdf_native.c
@@ -65,6 +65,7 @@ static jclass cls_IOException;
 static jclass cls_Link;
 static jclass cls_Matrix;
 static jclass cls_NativeDevice;
+static jclass cls_NullPointerException;
 static jclass cls_Object;
 static jclass cls_Outline;
 static jclass cls_OutOfMemoryError;
@@ -231,6 +232,11 @@ static void jni_throw_io(JNIEnv *env, const char *info)
 	(*env)->ThrowNew(env, cls_IOException, info);
 }
 
+static void jni_throw_null(JNIEnv *env, const char *info)
+{
+	(*env)->ThrowNew(env, cls_NullPointerException, info);
+}
+
 /* Convert a java exception and throw into fitz. */
 
 static void fz_throw_java(fz_context *ctx, JNIEnv *env)
@@ -511,6 +517,7 @@ static int find_fids(JNIEnv *env)
 	cls_IndexOutOfBoundsException = get_class(&err, env, "java/lang/IndexOutOfBoundsException");
 	cls_IllegalArgumentException = get_class(&err, env, "java/lang/IllegalArgumentException");
 	cls_IOException = get_class(&err, env, "java/io/IOException");
+	cls_NullPointerException = get_class(&err, env, "java/lang/NullPointerException");
 	cls_RuntimeException = get_class(&err, env, "java/lang/RuntimeException");
 
 	cls_OutOfMemoryError = get_class(&err, env, "java/lang/OutOfMemoryError");
@@ -536,6 +543,7 @@ static void lose_fids(JNIEnv *env)
 	(*env)->DeleteGlobalRef(env, cls_Link);
 	(*env)->DeleteGlobalRef(env, cls_Matrix);
 	(*env)->DeleteGlobalRef(env, cls_NativeDevice);
+	(*env)->DeleteGlobalRef(env, cls_NullPointerException);
 	(*env)->DeleteGlobalRef(env, cls_Object);
 	(*env)->DeleteGlobalRef(env, cls_Outline);
 	(*env)->DeleteGlobalRef(env, cls_OutOfMemoryError);
@@ -1169,122 +1177,182 @@ static inline fz_rect from_Rect(JNIEnv *env, jobject jrect)
 
 static inline fz_annot *from_Annotation(JNIEnv *env, jobject jobj)
 {
+	fz_annot *annot;
 	if (!jobj) return NULL;
-	return CAST(fz_annot *, (*env)->GetLongField(env, jobj, fid_Annot_pointer));
+	annot = CAST(fz_annot *, (*env)->GetLongField(env, jobj, fid_Annot_pointer));
+	if (!annot) jni_throw_null(env, "cannot use already destroyed object");
+	return annot;
 }
 
 static inline fz_buffer *from_Buffer(JNIEnv *env, jobject jobj)
 {
+	fz_buffer *buffer;
 	if (!jobj) return NULL;
-	return CAST(fz_buffer *, (*env)->GetLongField(env, jobj, fid_Buffer_pointer));
+	buffer = CAST(fz_buffer *, (*env)->GetLongField(env, jobj, fid_Buffer_pointer));
+	if (!buffer) jni_throw_null(env, "cannot use already destroyed object");
+	return buffer;
 }
 
 static inline fz_colorspace *from_ColorSpace(JNIEnv *env, jobject jobj)
 {
+	fz_colorspace *cs;
 	if (!jobj) return NULL;
-	return CAST(fz_colorspace *, (*env)->GetLongField(env, jobj, fid_ColorSpace_pointer));
+	cs = CAST(fz_colorspace *, (*env)->GetLongField(env, jobj, fid_ColorSpace_pointer));
+	if (!cs) jni_throw_null(env, "cannot use already destroyed object");
+	return cs;
 }
 
 static inline fz_cookie *from_Cookie(JNIEnv *env, jobject jobj)
 {
+	fz_cookie *cookie;
 	if (!jobj) return NULL;
-	return CAST(fz_cookie *, (*env)->GetLongField(env, jobj, fid_Cookie_pointer));
+	cookie = CAST(fz_cookie *, (*env)->GetLongField(env, jobj, fid_Cookie_pointer));
+	if (!cookie) jni_throw_null(env, "cannot use already destroyed object");
+	return cookie;
 }
 
 static fz_device *from_Device(JNIEnv *env, jobject jobj)
 {
+	fz_device *dev;
 	if (!jobj) return NULL;
-	return CAST(fz_device *, (*env)->GetLongField(env, jobj, fid_Device_pointer));
+	dev = CAST(fz_device *, (*env)->GetLongField(env, jobj, fid_Device_pointer));
+	if (!dev) jni_throw_null(env, "cannot use already destroyed object");
+	return dev;
 }
 
 static inline fz_display_list *from_DisplayList(JNIEnv *env, jobject jobj)
 {
+	fz_display_list *list;
 	if (!jobj) return NULL;
-	return CAST(fz_display_list *, (*env)->GetLongField(env, jobj, fid_DisplayList_pointer));
+	list = CAST(fz_display_list *, (*env)->GetLongField(env, jobj, fid_DisplayList_pointer));
+	if (!list) jni_throw_null(env, "cannot use already destroyed object");
+	return list;
 }
 
 static inline fz_document *from_Document(JNIEnv *env, jobject jobj)
 {
+	fz_document *doc;
 	if (!jobj) return NULL;
-	return CAST(fz_document *, (*env)->GetLongField(env, jobj, fid_Document_pointer));
+	doc = CAST(fz_document *, (*env)->GetLongField(env, jobj, fid_Document_pointer));
+	if (!doc) jni_throw_null(env, "cannot use already destroyed object");
+	return doc;
 }
 
 static inline fz_document_writer *from_DocumentWriter(JNIEnv *env, jobject jobj)
 {
+	fz_document_writer *wri;
 	if (!jobj) return NULL;
-	return CAST(fz_document_writer *, (*env)->GetLongField(env, jobj, fid_DocumentWriter_pointer));
+	wri = CAST(fz_document_writer *, (*env)->GetLongField(env, jobj, fid_DocumentWriter_pointer));
+	if (!wri) jni_throw_null(env, "cannot use already destroyed object");
+	return wri;
 }
 
 static inline fz_font *from_Font(JNIEnv *env, jobject jobj)
 {
+	fz_font *font;
 	if (!jobj) return NULL;
-	return CAST(fz_font *, (*env)->GetLongField(env, jobj, fid_Font_pointer));
+	font = CAST(fz_font *, (*env)->GetLongField(env, jobj, fid_Font_pointer));
+	if (!font) jni_throw_null(env, "cannot use already destroyed object");
+	return font;
 }
 
 static inline fz_image *from_Image(JNIEnv *env, jobject jobj)
 {
+	fz_image *image;
 	if (!jobj) return NULL;
-	return CAST(fz_image *, (*env)->GetLongField(env, jobj, fid_Image_pointer));
+	image = CAST(fz_image *, (*env)->GetLongField(env, jobj, fid_Image_pointer));
+	if (!image) jni_throw_null(env, "cannot use already destroyed object");
+	return image;
 }
 
 static inline fz_page *from_Page(JNIEnv *env, jobject jobj)
 {
+	fz_page *page;
 	if (!jobj) return NULL;
-	return CAST(fz_page *, (*env)->GetLongField(env, jobj, fid_Page_pointer));
+	page = CAST(fz_page *, (*env)->GetLongField(env, jobj, fid_Page_pointer));
+	if (!page) jni_throw_null(env, "cannot use already destroyed object");
+	return page;
 }
 
 static inline fz_path *from_Path(JNIEnv *env, jobject jobj)
 {
+	fz_path *path;
 	if (!jobj) return NULL;
-	return CAST(fz_path *, (*env)->GetLongField(env, jobj, fid_Path_pointer));
+	path = CAST(fz_path *, (*env)->GetLongField(env, jobj, fid_Path_pointer));
+	if (!path) jni_throw_null(env, "cannot use already destroyed object");
+	return path;
 }
 
 static inline pdf_document *from_PDFDocument(JNIEnv *env, jobject jobj)
 {
+	pdf_document *pdf;
 	if (!jobj) return NULL;
-	return CAST(pdf_document *, (*env)->GetLongField(env, jobj, fid_PDFDocument_pointer));
+	pdf = CAST(pdf_document *, (*env)->GetLongField(env, jobj, fid_PDFDocument_pointer));
+	if (!pdf) jni_throw_null(env, "cannot use already destroyed object");
+	return pdf;
 }
 
 static inline pdf_graft_map *from_PDFGraftMap(JNIEnv *env, jobject jobj)
 {
+	pdf_graft_map *map;
 	if (!jobj) return NULL;
-	return CAST(pdf_graft_map *, (*env)->GetLongField(env, jobj, fid_PDFGraftMap_pointer));
+	map = CAST(pdf_graft_map *, (*env)->GetLongField(env, jobj, fid_PDFGraftMap_pointer));
+	if (!map) jni_throw_null(env, "cannot use already destroyed object");
+	return map;
 }
 
 static inline pdf_obj *from_PDFObject(JNIEnv *env, jobject jobj)
 {
+	pdf_obj *obj;
 	if (!jobj) return NULL;
-	return CAST(pdf_obj *, (*env)->GetLongField(env, jobj, fid_PDFObject_pointer));
+	obj = CAST(pdf_obj *, (*env)->GetLongField(env, jobj, fid_PDFObject_pointer));
+	if (!obj) jni_throw_null(env, "cannot use already destroyed object");
+	return obj;
 }
 
 static inline fz_pixmap *from_Pixmap(JNIEnv *env, jobject jobj)
 {
+	fz_pixmap *pixmap;
 	if (!jobj) return NULL;
-	return CAST(fz_pixmap *, (*env)->GetLongField(env, jobj, fid_Pixmap_pointer));
+	pixmap = CAST(fz_pixmap *, (*env)->GetLongField(env, jobj, fid_Pixmap_pointer));
+	if (!pixmap) jni_throw_null(env, "cannot use already destroyed object");
+	return pixmap;
 }
 
 static inline fz_shade *from_Shade(JNIEnv *env, jobject jobj)
 {
+	fz_shade *shd;
 	if (!jobj) return NULL;
-	return CAST(fz_shade *, (*env)->GetLongField(env, jobj, fid_Shade_pointer));
+	shd = CAST(fz_shade *, (*env)->GetLongField(env, jobj, fid_Shade_pointer));
+	if (!shd) jni_throw_null(env, "cannot use already destroyed object");
+	return shd;
 }
 
 static inline fz_stroke_state *from_StrokeState(JNIEnv *env, jobject jobj)
 {
+	fz_stroke_state *stroke;
 	if (!jobj) return NULL;
-	return CAST(fz_stroke_state *, (*env)->GetLongField(env, jobj, fid_StrokeState_pointer));
+	stroke = CAST(fz_stroke_state *, (*env)->GetLongField(env, jobj, fid_StrokeState_pointer));
+	if (!stroke) jni_throw_null(env, "cannot use already destroyed object");
+	return stroke;
 }
 
 static inline fz_stext_page *from_StructuredText(JNIEnv *env, jobject jobj)
 {
+	fz_stext_page *stext;
 	if (!jobj) return NULL;
-	return CAST(fz_stext_page *, (*env)->GetLongField(env, jobj, fid_StructuredText_pointer));
+	stext = CAST(fz_stext_page *, (*env)->GetLongField(env, jobj, fid_StructuredText_pointer));
+	if (!stext) jni_throw_null(env, "cannot use already destroyed object");
+	return stext;
 }
 
 static inline fz_text *from_Text(JNIEnv *env, jobject jobj)
 {
+	fz_text *text;
 	if (!jobj) return NULL;
-	return CAST(fz_text *, (*env)->GetLongField(env, jobj, fid_Text_pointer));
+	text = CAST(fz_text *, (*env)->GetLongField(env, jobj, fid_Text_pointer));
+	if (!text) jni_throw_null(env, "cannot use already destroyed object");
+	return text;
 }
 
 /*
@@ -1671,7 +1739,7 @@ FUN(Device_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_device *dev = from_Device(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 
 	fz_drop_device(ctx, dev);
 }
@@ -1758,7 +1826,7 @@ FUN(NativeDevice_close)(JNIEnv *env, jobject self)
 	fz_device *dev = from_Device(env, self);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 
 	info = lockNativeDevice(env, self);
 	fz_try(ctx)
@@ -1780,7 +1848,7 @@ FUN(NativeDevice_fillPath)(JNIEnv *env, jobject self, jobject jpath, jboolean ev
 	float color[FZ_MAX_COLORS];
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!path) { jni_throw_arg(env, "path must not be null"); return; }
 	if (!from_jfloatArray(env, color, cs ? cs->n : FZ_MAX_COLORS, jcolor)) return;
 
@@ -1805,7 +1873,7 @@ FUN(NativeDevice_strokePath)(JNIEnv *env, jobject self, jobject jpath, jobject j
 	float color[FZ_MAX_COLORS];
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!path) { jni_throw_arg(env, "path must not be null"); return; }
 	if (!stroke) { jni_throw_arg(env, "stroke must not be null"); return; }
 	if (!from_jfloatArray(env, color, cs ? cs->n : FZ_MAX_COLORS, jcolor)) return;
@@ -1828,7 +1896,7 @@ FUN(NativeDevice_clipPath)(JNIEnv *env, jobject self, jobject jpath, jboolean ev
 	fz_matrix ctm = from_Matrix(env, jctm);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!path) { jni_throw_arg(env, "path must not be null"); return; }
 
 	info = lockNativeDevice(env, self);
@@ -1850,7 +1918,7 @@ FUN(NativeDevice_clipStrokePath)(JNIEnv *env, jobject self, jobject jpath, jobje
 	fz_matrix ctm = from_Matrix(env, jctm);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!path) { jni_throw_arg(env, "path must not be null"); return; }
 	if (!stroke) { jni_throw_arg(env, "stroke must not be null"); return; }
 
@@ -1874,7 +1942,7 @@ FUN(NativeDevice_fillText)(JNIEnv *env, jobject self, jobject jtext, jobject jct
 	float color[FZ_MAX_COLORS];
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!text) { jni_throw_arg(env, "text must not be null"); return; }
 	if (!from_jfloatArray(env, color, cs ? cs->n : FZ_MAX_COLORS, jcolor)) return;
 
@@ -1899,7 +1967,7 @@ FUN(NativeDevice_strokeText)(JNIEnv *env, jobject self, jobject jtext, jobject j
 	float color[FZ_MAX_COLORS];
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!text) { jni_throw_arg(env, "text must not be null"); return; }
 	if (!stroke) { jni_throw_arg(env, "stroke must not be null"); return; }
 	if (!from_jfloatArray(env, color, cs ? cs->n : FZ_MAX_COLORS, jcolor)) return;
@@ -1922,7 +1990,7 @@ FUN(NativeDevice_clipText)(JNIEnv *env, jobject self, jobject jtext, jobject jct
 	fz_matrix ctm = from_Matrix(env, jctm);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!text) { jni_throw_arg(env, "text must not be null"); return; }
 
 	info = lockNativeDevice(env, self);
@@ -1944,7 +2012,7 @@ FUN(NativeDevice_clipStrokeText)(JNIEnv *env, jobject self, jobject jtext, jobje
 	fz_matrix ctm = from_Matrix(env, jctm);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!text) { jni_throw_arg(env, "text must not be null"); return; }
 	if (!stroke) { jni_throw_arg(env, "stroke must not be null"); return; }
 
@@ -1966,7 +2034,7 @@ FUN(NativeDevice_ignoreText)(JNIEnv *env, jobject self, jobject jtext, jobject j
 	fz_matrix ctm = from_Matrix(env, jctm);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!text) { jni_throw_arg(env, "text must not be null"); return; }
 
 	info = lockNativeDevice(env, self);
@@ -1987,7 +2055,7 @@ FUN(NativeDevice_fillShade)(JNIEnv *env, jobject self, jobject jshd, jobject jct
 	fz_matrix ctm = from_Matrix(env, jctm);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!shd) { jni_throw_arg(env, "shade must not be null"); return; }
 
 	info = lockNativeDevice(env, self);
@@ -2008,7 +2076,7 @@ FUN(NativeDevice_fillImage)(JNIEnv *env, jobject self, jobject jimg, jobject jct
 	fz_matrix ctm = from_Matrix(env, jctm);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!img) { jni_throw_arg(env, "image must not be null"); return; }
 
 	info = lockNativeDevice(env, self);
@@ -2031,7 +2099,7 @@ FUN(NativeDevice_fillImageMask)(JNIEnv *env, jobject self, jobject jimg, jobject
 	float color[FZ_MAX_COLORS];
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!img) { jni_throw_arg(env, "image must not be null"); return; }
 	if (!from_jfloatArray(env, color, cs ? cs->n : FZ_MAX_COLORS, jcolor)) return;
 
@@ -2053,7 +2121,7 @@ FUN(NativeDevice_clipImageMask)(JNIEnv *env, jobject self, jobject jimg, jobject
 	fz_matrix ctm = from_Matrix(env, jctm);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!img) { jni_throw_arg(env, "image must not be null"); return; }
 
 	info = lockNativeDevice(env, self);
@@ -2072,7 +2140,7 @@ FUN(NativeDevice_popClip)(JNIEnv *env, jobject self)
 	fz_device *dev = from_Device(env, self);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 
 	info = lockNativeDevice(env, self);
 	fz_try(ctx)
@@ -2093,7 +2161,7 @@ FUN(NativeDevice_beginMask)(JNIEnv *env, jobject self, jobject jrect, jboolean l
 	float color[FZ_MAX_COLORS];
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 	if (!from_jfloatArray(env, color, cs ? cs->n : FZ_MAX_COLORS, jcolor)) return;
 
 	info = lockNativeDevice(env, self);
@@ -2112,7 +2180,7 @@ FUN(NativeDevice_endMask)(JNIEnv *env, jobject self)
 	fz_device *dev = from_Device(env, self);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 
 	info = lockNativeDevice(env, self);
 	fz_try(ctx)
@@ -2131,7 +2199,7 @@ FUN(NativeDevice_beginGroup)(JNIEnv *env, jobject self, jobject jrect, jboolean
 	fz_rect rect = from_Rect(env, jrect);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 
 	info = lockNativeDevice(env, self);
 	fz_try(ctx)
@@ -2149,7 +2217,7 @@ FUN(NativeDevice_endGroup)(JNIEnv *env, jobject self)
 	fz_device *dev = from_Device(env, self);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 
 	info = lockNativeDevice(env, self);
 	fz_try(ctx)
@@ -2171,7 +2239,7 @@ FUN(NativeDevice_beginTile)(JNIEnv *env, jobject self, jobject jarea, jobject jv
 	NativeDeviceInfo *info;
 	int i = 0;
 
-	if (!ctx) return 0;
+	if (!ctx || !dev) return 0;
 
 	info = lockNativeDevice(env, self);
 	fz_try(ctx)
@@ -2194,7 +2262,7 @@ FUN(NativeDevice_endTile)(JNIEnv *env, jobject self)
 	fz_device *dev = from_Device(env, self);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !dev) return;
 
 	info = lockNativeDevice(env, self);
 	fz_try(ctx)
@@ -2435,7 +2503,7 @@ FUN(ColorSpace_finalize)(JNIEnv *env, jobject self)
 {
 	fz_context *ctx = get_context(env);
 	fz_colorspace *cs = from_ColorSpace(env, self);
-	if (!ctx) return;
+	if (!ctx || !cs) return;
 	fz_drop_colorspace(ctx, cs);
 }
 
@@ -2443,7 +2511,7 @@ JNIEXPORT jint JNICALL
 FUN(ColorSpace_getNumberOfComponents)(JNIEnv *env, jobject self)
 {
 	fz_colorspace *cs = from_ColorSpace(env, self);
-	return cs->n;
+	return cs ? cs->n : 0;
 }
 
 JNIEXPORT jlong JNICALL
@@ -2486,7 +2554,7 @@ FUN(Font_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_font *font = from_Font(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !font) return;
 
 	fz_drop_font(ctx, font);
 }
@@ -2534,7 +2602,7 @@ FUN(Font_getName)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_font *font = from_Font(env, self);
 
-	if (!ctx) return NULL;
+	if (!ctx || !font) return NULL;
 
 	return (*env)->NewStringUTF(env, font->name);
 }
@@ -2546,7 +2614,7 @@ FUN(Font_encodeCharacter)(JNIEnv *env, jobject self, jint unicode)
 	fz_font *font = from_Font(env, self);
 	jint glyph = 0;
 
-	if (!ctx) return 0;
+	if (!ctx || !font) return 0;
 
 	fz_try(ctx)
 		glyph = fz_encode_character(ctx, font, unicode);
@@ -2566,7 +2634,7 @@ FUN(Font_advanceGlyph)(JNIEnv *env, jobject self, jint glyph, jboolean wmode)
 	fz_font *font = from_Font(env, self);
 	float advance = 0;
 
-	if (!ctx) return 0;
+	if (!ctx || !font) return 0;
 
 	fz_try(ctx)
 		advance = fz_advance_glyph(ctx, font, glyph, wmode);
@@ -2587,7 +2655,7 @@ FUN(Pixmap_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_pixmap *pixmap = from_Pixmap(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !pixmap) return;
 
 	fz_drop_pixmap(ctx, pixmap);
 }
@@ -2622,7 +2690,7 @@ FUN(Pixmap_clear)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_pixmap *pixmap = from_Pixmap(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !pixmap) return;
 
 	fz_try(ctx)
 		fz_clear_pixmap(ctx, pixmap);
@@ -2636,7 +2704,7 @@ FUN(Pixmap_clearWithValue)(JNIEnv *env, jobject self, jint value)
 	fz_context *ctx = get_context(env);
 	fz_pixmap *pixmap = from_Pixmap(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !pixmap) return;
 
 	fz_try(ctx)
 		fz_clear_pixmap_with_value(ctx, pixmap, value);
@@ -2648,49 +2716,49 @@ JNIEXPORT jint JNICALL
 FUN(Pixmap_getX)(JNIEnv *env, jobject self)
 {
 	fz_pixmap *pixmap = from_Pixmap(env, self);
-	return pixmap->x;
+	return pixmap ? pixmap->x : 0;
 }
 
 JNIEXPORT jint JNICALL
 FUN(Pixmap_getY)(JNIEnv *env, jobject self)
 {
 	fz_pixmap *pixmap = from_Pixmap(env, self);
-	return pixmap->y;
+	return pixmap ? pixmap->y : 0;
 }
 
 JNIEXPORT jint JNICALL
 FUN(Pixmap_getWidth)(JNIEnv *env, jobject self)
 {
 	fz_pixmap *pixmap = from_Pixmap(env, self);
-	return pixmap->w;
+	return pixmap ? pixmap->w : 0;
 }
 
 JNIEXPORT jint JNICALL
 FUN(Pixmap_getHeight)(JNIEnv *env, jobject self)
 {
 	fz_pixmap *pixmap = from_Pixmap(env, self);
-	return pixmap->h;
+	return pixmap ? pixmap->h : 0;
 }
 
 JNIEXPORT jint JNICALL
 FUN(Pixmap_getNumberOfComponents)(JNIEnv *env, jobject self)
 {
 	fz_pixmap *pixmap = from_Pixmap(env, self);
-	return pixmap->n;
+	return pixmap ? pixmap->n : 0;
 }
 
 JNIEXPORT jboolean JNICALL
 FUN(Pixmap_getAlpha)(JNIEnv *env, jobject self)
 {
 	fz_pixmap *pixmap = from_Pixmap(env, self);
-	return pixmap->alpha ? JNI_TRUE : JNI_FALSE;
+	return pixmap && pixmap->alpha ? JNI_TRUE : JNI_FALSE;
 }
 
 JNIEXPORT jint JNICALL
 FUN(Pixmap_getStride)(JNIEnv *env, jobject self)
 {
 	fz_pixmap *pixmap = from_Pixmap(env, self);
-	return pixmap->stride;
+	return pixmap ? pixmap->stride : 0;
 }
 
 JNIEXPORT jobject JNICALL
@@ -2700,7 +2768,7 @@ FUN(Pixmap_getColorSpace)(JNIEnv *env, jobject self)
 	fz_pixmap *pixmap = from_Pixmap(env, self);
 	fz_colorspace *cs;
 
-	if (!ctx) return NULL;
+	if (!ctx | !pixmap) return NULL;
 
 	fz_try(ctx)
 		cs = fz_pixmap_colorspace(ctx, pixmap);
@@ -2721,7 +2789,7 @@ FUN(Pixmap_getSamples)(JNIEnv *env, jobject self)
 	int size = pixmap->h * pixmap->stride;
 	jbyteArray arr;
 
-	if (!ctx) return NULL;
+	if (!ctx | !pixmap) return NULL;
 
 	arr = (*env)->NewByteArray(env, size);
 	if (!arr) return NULL;
@@ -2738,7 +2806,7 @@ FUN(Pixmap_getSample)(JNIEnv *env, jobject self, jint x, jint y, jint k)
 	fz_context *ctx = get_context(env);
 	fz_pixmap *pixmap = from_Pixmap(env, self);
 
-	if (!ctx) return 0;
+	if (!ctx | !pixmap) return 0;
 
 	if (x < 0 || x >= pixmap->w) { jni_throw_oob(env, "x out of range"); return 0; }
 	if (y < 0 || y >= pixmap->h) { jni_throw_oob(env, "y out of range"); return 0; }
@@ -2755,7 +2823,7 @@ FUN(Pixmap_getPixels)(JNIEnv *env, jobject self)
 	int size = pixmap->w * pixmap->h;
 	jintArray arr;
 
-	if (!ctx) return NULL;
+	if (!ctx | !pixmap) return NULL;
 
 	if (pixmap->n != 4 || !pixmap->alpha)
 	{
@@ -2782,14 +2850,14 @@ JNIEXPORT jint JNICALL
 FUN(Pixmap_getXResolution)(JNIEnv *env, jobject self)
 {
 	fz_pixmap *pixmap = from_Pixmap(env, self);
-	return pixmap->xres;
+	return pixmap ? pixmap->xres : 0;
 }
 
 JNIEXPORT jint JNICALL
 FUN(Pixmap_getYResolution)(JNIEnv *env, jobject self)
 {
 	fz_pixmap *pixmap = from_Pixmap(env, self);
-	return pixmap->yres;
+	return pixmap ? pixmap->yres : 0;
 }
 
 /* Path Interface */
@@ -2800,7 +2868,7 @@ FUN(Path_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_path *path = from_Path(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !path) return;
 
 	fz_drop_path(ctx, path);
 }
@@ -2831,7 +2899,7 @@ FUN(Path_currentPoint)(JNIEnv *env, jobject self)
 	fz_path *path = from_Path(env, self);
 	fz_point point;
 
-	if (!ctx) return NULL;
+	if (!ctx || !path) return NULL;
 
 	fz_try(ctx)
 		point = fz_currentpoint(ctx, path);
@@ -2850,7 +2918,7 @@ FUN(Path_moveTo)(JNIEnv *env, jobject self, jfloat x, jfloat y)
 	fz_context *ctx = get_context(env);
 	fz_path *path = from_Path(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !path) return;
 
 	fz_try(ctx)
 		fz_moveto(ctx, path, x, y);
@@ -2864,7 +2932,7 @@ FUN(Path_lineTo)(JNIEnv *env, jobject self, jfloat x, jfloat y)
 	fz_context *ctx = get_context(env);
 	fz_path *path = from_Path(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !path) return;
 
 	fz_try(ctx)
 		fz_lineto(ctx, path, x, y);
@@ -2878,7 +2946,7 @@ FUN(Path_curveTo)(JNIEnv *env, jobject self, jfloat cx1, jfloat cy1, jfloat cx2,
 	fz_context *ctx = get_context(env);
 	fz_path *path = from_Path(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !path) return;
 
 	fz_try(ctx)
 		fz_curveto(ctx, path, cx1, cy1, cx2, cy2, ex, ey);
@@ -2892,7 +2960,7 @@ FUN(Path_curveToV)(JNIEnv *env, jobject self, jfloat cx, jfloat cy, jfloat ex, j
 	fz_context *ctx = get_context(env);
 	fz_path *path = from_Path(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !path) return;
 
 	fz_try(ctx)
 		fz_curvetov(ctx, path, cx, cy, ex, ey);
@@ -2906,7 +2974,7 @@ FUN(Path_curveToY)(JNIEnv *env, jobject self, jfloat cx, jfloat cy, jfloat ex, j
 	fz_context *ctx = get_context(env);
 	fz_path *path = from_Path(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !path) return;
 
 	fz_try(ctx)
 		fz_curvetoy(ctx, path, cx, cy, ex, ey);
@@ -2920,7 +2988,7 @@ FUN(Path_rect)(JNIEnv *env, jobject self, jint x1, jint y1, jint x2, jint y2)
 	fz_context *ctx = get_context(env);
 	fz_path *path = from_Path(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !path) return;
 
 	fz_try(ctx)
 		fz_rectto(ctx, path, x1, y1, x2, y2);
@@ -2934,7 +3002,7 @@ FUN(Path_closePath)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_path *path = from_Path(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !path) return;
 
 	fz_try(ctx)
 		fz_closepath(ctx, path);
@@ -2949,7 +3017,7 @@ FUN(Path_transform)(JNIEnv *env, jobject self, jobject jctm)
 	fz_path *path = from_Path(env, self);
 	fz_matrix ctm = from_Matrix(env, jctm);
 
-	if (!ctx) return;
+	if (!ctx || !path) return;
 
 	fz_try(ctx)
 		fz_transform_path(ctx, path, &ctm);
@@ -2964,7 +3032,7 @@ FUN(Path_cloneNative)(JNIEnv *env, jobject self)
 	fz_path *old_path = from_Path(env, self);
 	fz_path *new_path = NULL;
 
-	if (!ctx) return 0;
+	if (!ctx || !old_path) return 0;
 
 	fz_try(ctx)
 		new_path = fz_clone_path(ctx, old_path);
@@ -2986,7 +3054,7 @@ FUN(Path_getBounds)(JNIEnv *env, jobject self, jobject jstroke, jobject jctm)
 	fz_matrix ctm = from_Matrix(env, jctm);
 	fz_rect rect;
 
-	if (!ctx) return NULL;
+	if (!ctx || !path) return NULL;
 	if (!stroke) { jni_throw_arg(env, "stroke must not be null"); return NULL; }
 
 	fz_try(ctx)
@@ -3065,7 +3133,7 @@ FUN(Path_walk)(JNIEnv *env, jobject self, jobject obj)
 	fz_path *path = from_Path(env, self);
 	path_walker_state state;
 
-	if (!ctx) return;
+	if (!ctx || !path) return;
 	if (!obj) { jni_throw_arg(env, "object must not be null"); return; }
 
 	state.env = env;
@@ -3085,7 +3153,7 @@ FUN(StrokeState_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_stroke_state *stroke = from_StrokeState(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !stroke) return;
 
 	fz_drop_stroke_state(ctx, stroke);
 }
@@ -3182,7 +3250,7 @@ FUN(StrokeState_getDashes)(JNIEnv *env, jobject self)
 	fz_stroke_state *stroke = from_StrokeState(env, self);
 	jfloatArray arr;
 
-	if (!ctx) return NULL;
+	if (!ctx || !stroke) return NULL;
 	if (!stroke) { jni_throw_arg(env, "stroke must not be null"); return NULL; }
 
 	if (stroke->dash_len == 0)
@@ -3205,7 +3273,7 @@ FUN(Text_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_text *text = from_Text(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !text) return;
 
 	fz_drop_text(ctx, text);
 }
@@ -3217,7 +3285,7 @@ FUN(Text_clone)(JNIEnv *env, jobject self)
 	fz_text *old_text = from_Text(env, self);
 	fz_text *new_text = NULL;
 
-	if (!ctx) return 0;
+	if (!ctx || !old_text) return 0;
 
 	fz_try(ctx)
 		new_text = fz_clone_text(ctx, old_text);
@@ -3258,7 +3326,7 @@ FUN(Text_getBounds)(JNIEnv *env, jobject self, jobject jstroke, jobject jctm)
 	fz_matrix ctm = from_Matrix(env, jctm);
 	fz_rect rect;
 
-	if (!ctx) return NULL;
+	if (!ctx || !text) return NULL;
 	if (!stroke) { jni_throw_arg(env, "stroke must not be null"); return NULL; }
 
 	fz_try(ctx)
@@ -3280,7 +3348,7 @@ FUN(Text_showGlyph)(JNIEnv *env, jobject self, jobject jfont, jobject jtrm, jint
 	fz_font *font = from_Font(env, jfont);
 	fz_matrix trm = from_Matrix(env, jtrm);
 
-	if (!ctx) return;
+	if (!ctx || !text) return;
 	if (!font) { jni_throw_arg(env, "font must not be null"); return; }
 
 	fz_try(ctx)
@@ -3298,7 +3366,7 @@ FUN(Text_showString)(JNIEnv *env, jobject self, jobject jfont, jobject jtrm, jst
 	fz_matrix trm = from_Matrix(env, jtrm);
 	const char *str = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !text) return;
 	if (!jfont) { jni_throw_arg(env, "font must not be null"); return; }
 	if (!jstr) { jni_throw_arg(env, "string must not be null"); return; }
 
@@ -3330,7 +3398,7 @@ FUN(Text_walk)(JNIEnv *env, jobject self, jobject walker)
 	jobject jtrm = NULL;
 	int i;
 
-	if (!ctx) return;
+	if (!ctx || !text) return;
 	if (!walker) { jni_throw_arg(env, "walker must not be null"); return; }
 
 	if (text->head == NULL)
@@ -3380,7 +3448,7 @@ FUN(Image_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_image *image = from_Image(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !image) return;
 
 	fz_drop_image(ctx, image);
 }
@@ -3458,9 +3526,7 @@ FUN(Image_getColorSpace)(JNIEnv *env, jobject self)
 {
 	fz_context *ctx = get_context(env);
 	fz_image *image = from_Image(env, self);
-
-	if (!ctx) return NULL;
-
+	if (!ctx || !image) return NULL;
 	return to_ColorSpace_safe(ctx, env, image->colorspace);
 }
 
@@ -3489,16 +3555,14 @@ JNIEXPORT jboolean JNICALL
 FUN(Image_getImageMask)(JNIEnv *env, jobject self)
 {
 	fz_image *image = from_Image(env, self);
-	if (!image) return JNI_FALSE;
-	return image->imagemask ? JNI_TRUE : JNI_FALSE;
+	return image && image->imagemask ? JNI_TRUE : JNI_FALSE;
 }
 
 JNIEXPORT jboolean JNICALL
 FUN(Image_getInterpolate)(JNIEnv *env, jobject self)
 {
 	fz_image *image = from_Image(env, self);
-	if (!image) return JNI_FALSE;
-	return image->interpolate ? JNI_TRUE : JNI_FALSE;
+	return image && image->interpolate ? JNI_TRUE : JNI_FALSE;
 }
 
 JNIEXPORT jobject JNICALL
@@ -3507,7 +3571,7 @@ FUN(Image_getMask)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_image *img = from_Image(env, self);
 
-	if (!ctx) return NULL;
+	if (!ctx || !img) return NULL;
 
 	return to_Image_safe(ctx, env, img->mask);
 }
@@ -3519,7 +3583,7 @@ FUN(Image_toPixmap)(JNIEnv *env, jobject self)
 	fz_image *img = from_Image(env, self);
 	fz_pixmap *pixmap = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !img) return NULL;
 
 	fz_try(ctx)
 		pixmap = fz_get_pixmap_from_image(ctx, img, NULL, NULL, NULL, NULL);
@@ -3540,7 +3604,7 @@ FUN(Annotation_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_annot *annot = from_Annotation(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !annot) return;
 
 	fz_drop_annot(ctx, annot);
 }
@@ -3555,7 +3619,7 @@ FUN(Annotation_run)(JNIEnv *env, jobject self, jobject jdev, jobject jctm, jobje
 	fz_cookie *cookie= from_Cookie(env, jcookie);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !annot) return;
 	if (!dev) { jni_throw_arg(env, "device must not be null"); return; }
 
 	info = lockNativeDevice(env, jdev);
@@ -3573,7 +3637,7 @@ FUN(Annotation_advance)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_annot *annot = from_Annotation(env, self);
 
-	if (!ctx) return 0;
+	if (!ctx || !annot) return 0;
 
 	fz_try(ctx)
 		annot = fz_next_annot(ctx, annot);
@@ -3595,7 +3659,7 @@ FUN(Annotation_toPixmap)(JNIEnv *env, jobject self, jobject jctm, jobject jcs, j
 	fz_colorspace *cs = from_ColorSpace(env, jcs);
 	fz_pixmap *pixmap = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !annot) return NULL;
 
 	fz_try(ctx)
 		pixmap = fz_new_pixmap_from_annot(ctx, annot, &ctm, cs, alpha);
@@ -3615,7 +3679,7 @@ FUN(Annotation_getBounds)(JNIEnv *env, jobject self)
 	fz_annot *annot = from_Annotation(env, self);
 	fz_rect rect;
 
-	if (!ctx) return NULL;
+	if (!ctx || !annot) return NULL;
 
 	fz_try(ctx)
 		fz_bound_annot(ctx, annot, &rect);
@@ -3635,7 +3699,7 @@ FUN(Annotation_toDisplayList)(JNIEnv *env, jobject self)
 	fz_annot *annot = from_Annotation(env, self);
 	fz_display_list *list = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !annot) return NULL;
 
 	fz_try(ctx)
 		list = fz_new_display_list_from_annot(ctx, annot);
@@ -3695,14 +3759,13 @@ FUN(Document_proofNative)(JNIEnv *env, jobject self, jstring jCurrentPath, jstri
 
 	fz_context *ctx = get_context(env);
 	fz_document *doc = from_Document(env, self);
-
 	char *tmp;
 	jstring ret;
 	const char *currentPath = NULL;
 	const char *printProfile = NULL;
 	const char *displayProfile = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !doc) return NULL;
 	if (!jCurrentPath) { jni_throw_arg(env, "currentPath must not be null"); return NULL; }
 	if (!jPrintProfile) { jni_throw_arg(env, "printProfile must not be null"); return NULL; }
 	if (!jDisplayProfile) { jni_throw_arg(env, "displayProfile must not be null"); return NULL; }
@@ -3765,7 +3828,7 @@ FUN(Document_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_document *doc = from_Document(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !doc) return;
 
 	fz_drop_document(ctx, doc);
 }
@@ -3805,7 +3868,7 @@ FUN(Document_needsPassword)(JNIEnv *env, jobject self)
 	fz_document *doc = from_Document(env, self);
 	int okay = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !doc) return JNI_FALSE;
 
 	fz_try(ctx)
 		okay = fz_needs_password(ctx, doc);
@@ -3826,7 +3889,7 @@ FUN(Document_authenticatePassword)(JNIEnv *env, jobject self, jstring jpassword)
 	const char *password = NULL;
 	int okay = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !doc) return JNI_FALSE;
 	if (password)
 	{
 		password = (*env)->GetStringUTFChars(env, jpassword, NULL);
@@ -3854,7 +3917,7 @@ FUN(Document_countPages)(JNIEnv *env, jobject self)
 	fz_document *doc = from_Document(env, self);
 	int count = 0;
 
-	if (!ctx) return 0;
+	if (!ctx || !doc) return 0;
 
 	fz_try(ctx)
 		count = fz_count_pages(ctx, doc);
@@ -3874,7 +3937,7 @@ FUN(Document_isReflowable)(JNIEnv *env, jobject self)
 	fz_document *doc = from_Document(env, self);
 	int is_reflowable = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !doc) return JNI_FALSE;
 
 	fz_try(ctx)
 		is_reflowable = fz_is_document_reflowable(ctx, doc);
@@ -3893,7 +3956,7 @@ FUN(Document_layout)(JNIEnv *env, jobject self, jfloat w, jfloat h, jfloat em)
 	fz_context *ctx = get_context(env);
 	fz_document *doc = from_Document(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !doc) return;
 
 	fz_try(ctx)
 		fz_layout_document(ctx, doc, w, h, em);
@@ -3908,7 +3971,7 @@ FUN(Document_loadPage)(JNIEnv *env, jobject self, jint number)
 	fz_document *doc = from_Document(env, self);
 	fz_page *page = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !doc) return NULL;
 
 	fz_try(ctx)
 		page = fz_load_page(ctx, doc, number);
@@ -3929,7 +3992,7 @@ FUN(Document_getMetaData)(JNIEnv *env, jobject self, jstring jkey)
 	const char *key = NULL;
 	char info[256];
 
-	if (!ctx) return NULL;
+	if (!ctx || !doc) return NULL;
 	if (!jkey) { jni_throw_arg(env, "key must not be null"); return NULL; }
 
 	key = (*env)->GetStringUTFChars(env, jkey, NULL);
@@ -3957,7 +4020,7 @@ FUN(Document_isUnencryptedPDF)(JNIEnv *env, jobject self)
 	pdf_document *idoc = pdf_specifics(ctx, doc);
 	int cryptVer;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !doc) return JNI_FALSE;
 	if (!idoc)
 		return JNI_FALSE;
 
@@ -3973,7 +4036,7 @@ FUN(Document_loadOutline)(JNIEnv *env, jobject self)
 	fz_outline *outline = NULL;
 	jobject joutline = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !doc) return NULL;
 
 	fz_var(outline);
 
@@ -4003,7 +4066,7 @@ FUN(Document_toPDFDocument)(JNIEnv *env, jobject self)
 	fz_document *doc = from_Document(env, self);
 	pdf_document *pdf = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !doc) return NULL;
 
 	fz_try(ctx)
 		pdf = pdf_specifics(ctx, doc);
@@ -4024,7 +4087,7 @@ FUN(Page_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_page *page = from_Page(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !page) return;
 
 	fz_drop_page(ctx, page);
 }
@@ -4036,7 +4099,7 @@ FUN(Page_countSeparations)(JNIEnv *env, jobject self)
 	fz_page *page = from_Page(env, self);
 	int nSep;
 
-	if (!ctx) return 0;
+	if (!ctx || !page) return 0;
 
 	fz_try(ctx)
 		nSep = fz_count_separations_on_page(ctx, page);
@@ -4055,7 +4118,7 @@ FUN(Page_enableSeparation)(JNIEnv *env, jobject self, int sep, jboolean enable)
 	fz_context *ctx = get_context(env);
 	fz_page *page = from_Page(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !page) return;
 
 	fz_try(ctx)
 		fz_control_separation_on_page(ctx, page, sep, !enable);
@@ -4068,14 +4131,13 @@ FUN(Page_getSeparation)(JNIEnv *env, jobject self, int sep)
 {
 	fz_context *ctx = get_context(env);
 	fz_page *page = from_Page(env, self);
-
 	const char *name;
 	char rgba[4];
 	unsigned int bgra;
 	unsigned int cmyk;
 	jobject jname;
 
-	if (!ctx) return NULL;
+	if (!ctx || !page) return NULL;
 
 	/* MuPDF returns RGBA as bytes. Android wants a packed BGRA int. */
 	name = fz_get_separation_on_page(ctx, page, sep, (unsigned int *)(&rgba[0]), &cmyk);
@@ -4094,7 +4156,7 @@ FUN(Page_toPixmap)(JNIEnv *env, jobject self, jobject jctm, jobject jcs, jboolea
 	fz_matrix ctm = from_Matrix(env, jctm);
 	fz_pixmap *pixmap = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !page) return NULL;
 
 	fz_try(ctx)
 		pixmap = fz_new_pixmap_from_page(ctx, page, &ctm, cs, alpha);
@@ -4114,7 +4176,7 @@ FUN(Page_getBounds)(JNIEnv *env, jobject self)
 	fz_page *page = from_Page(env, self);
 	fz_rect rect;
 
-	if (!ctx) return NULL;
+	if (!ctx || !page) return NULL;
 
 	fz_try(ctx)
 		fz_bound_page(ctx, page, &rect);
@@ -4137,7 +4199,7 @@ FUN(Page_run)(JNIEnv *env, jobject self, jobject jdev, jobject jctm, jobject jco
 	fz_cookie *cookie = from_Cookie(env, jcookie);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !page) return;
 	if (!dev) { jni_throw_arg(env, "device must not be null"); return; }
 
 	info = lockNativeDevice(env, jdev);
@@ -4159,7 +4221,7 @@ FUN(Page_runPageContents)(JNIEnv *env, jobject self, jobject jdev, jobject jctm,
 	fz_cookie *cookie = from_Cookie(env, jcookie);
 	NativeDeviceInfo *info;
 
-	if (!ctx) return;
+	if (!ctx || !page) return;
 	if (!dev) { jni_throw_arg(env, "device must not be null"); return; }
 
 	info = lockNativeDevice(env, jdev);
@@ -4182,7 +4244,7 @@ FUN(Page_getAnnotations)(JNIEnv *env, jobject self)
 	int annot_count;
 	int i;
 
-	if (!ctx) return NULL;
+	if (!ctx || !page) return NULL;
 
 	/* count the annotations */
 	fz_try(ctx)
@@ -4241,7 +4303,7 @@ FUN(Page_getLinks)(JNIEnv *env, jobject self)
 	int link_count;
 	int i;
 
-	if (!ctx) return NULL;
+	if (!ctx || !page) return NULL;
 
 	fz_var(links);
 
@@ -4316,7 +4378,7 @@ FUN(Page_search)(JNIEnv *env, jobject self, jstring jneedle)
 	const char *needle = NULL;
 	int n = 0;
 
-	if (!ctx) return NULL;
+	if (!ctx || !page) return NULL;
 	if (!jneedle) { jni_throw_arg(env, "needle must not be null"); return NULL; }
 
 	needle = (*env)->GetStringUTFChars(env, jneedle, NULL);
@@ -4342,7 +4404,7 @@ FUN(Page_toDisplayList)(JNIEnv *env, jobject self, jboolean no_annotations)
 	fz_page *page = from_Page(env, self);
 	fz_display_list *list = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !page) return NULL;
 
 	fz_try(ctx)
 		if (no_annotations)
@@ -4366,7 +4428,7 @@ FUN(Page_toStructuredText)(JNIEnv *env, jobject self, jint joptions)
 	fz_stext_sheet *sheet = NULL;
 	fz_stext_page *text = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !page) return NULL;
 
 	fz_var(sheet);
 
@@ -4391,7 +4453,6 @@ FUN(Page_textAsHtml)(JNIEnv *env, jobject self)
 {
 	fz_context *ctx = get_context(env);
 	fz_page *page = from_Page(env, self);
-
 	fz_stext_sheet *sheet = NULL;
 	fz_stext_page *text = NULL;
 	fz_device *dev = NULL;
@@ -4400,7 +4461,7 @@ FUN(Page_textAsHtml)(JNIEnv *env, jobject self)
 	fz_buffer *buf = NULL;
 	fz_output *out = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !page) return NULL;
 
 	fz_var(sheet);
 	fz_var(text);
@@ -4471,7 +4532,7 @@ FUN(Cookie_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_cookie *cookie = from_Cookie(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !cookie) return;
 
 	fz_free(ctx, cookie);
 }
@@ -4501,7 +4562,7 @@ FUN(Cookie_abort)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_cookie *cookie = from_Cookie(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !cookie) return;
 
 	cookie->abort = 1;
 }
@@ -4540,7 +4601,7 @@ FUN(DisplayList_run)(JNIEnv *env, jobject self, jobject jdev, jobject jctm, jobj
 	fz_rect local_rect;
 	fz_rect *rect = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !list) return;
 	if (!dev) { jni_throw_arg(env, "device must not be null"); return; }
 
 	/* Use a scissor rectangle if one is supplied */
@@ -4565,7 +4626,7 @@ FUN(DisplayList_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_display_list *list = from_DisplayList(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !list) return;
 
 	fz_drop_display_list(ctx, list);
 }
@@ -4579,7 +4640,7 @@ FUN(DisplayList_toPixmap)(JNIEnv *env, jobject self, jobject jctm, jobject jcs,
 	fz_colorspace *cs = from_ColorSpace(env, jcs);
 	fz_pixmap *pixmap = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !list) return NULL;
 
 	fz_try(ctx)
 		pixmap = fz_new_pixmap_from_display_list(ctx, list, &ctm, cs, alpha);
@@ -4600,7 +4661,7 @@ FUN(DisplayList_toStructuredText)(JNIEnv *env, jobject self, jint joptions)
 	fz_stext_sheet *sheet = NULL;
 	fz_stext_page *text = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !list) return NULL;
 
 	fz_var(sheet);
 
@@ -4629,7 +4690,7 @@ FUN(DisplayList_search)(JNIEnv *env, jobject self, jstring jneedle)
 	const char *needle = NULL;
 	int n = 0;
 
-	if (!ctx) return NULL;
+	if (!ctx || !list) return NULL;
 	if (!jneedle) { jni_throw_arg(env, "needle must not be null"); return NULL; }
 
 	needle = (*env)->GetStringUTFChars(env, jneedle, NULL);
@@ -4656,7 +4717,7 @@ FUN(Buffer_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_buffer *buf = from_Buffer(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !buf) return;
 
 	fz_drop_buffer(ctx, buf);
 }
@@ -4686,7 +4747,7 @@ FUN(Buffer_getLength)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_buffer *buf = from_Buffer(env, self);
 
-	if (!ctx) return -1;
+	if (!ctx || !buf) return -1;
 
 	return buf->len;
 }
@@ -4698,7 +4759,7 @@ FUN(Buffer_readByte)(JNIEnv *env, jobject self, jint jat)
 	fz_buffer *buf = from_Buffer(env, self);
 	size_t at = (size_t) jat;
 
-	if (!ctx) return -1;
+	if (!ctx || !buf) return -1;
 	if (jat < 0) { jni_throw_oob(env, "at is negative"); return -1; }
 
 	if (at >= buf->len)
@@ -4718,7 +4779,7 @@ FUN(Buffer_readBytes)(JNIEnv *env, jobject self, jint jat, jobject jbs)
 	size_t remaining_input = 0;
 	size_t remaining_output = 0;
 
-	if (!ctx) return -1;
+	if (!ctx || !buf) return -1;
 	if (jat < 0) { jni_throw_oob(env, "at is negative"); return -1; }
 	if (!jbs) { jni_throw_arg(env, "buffer must not be null"); return -1; }
 
@@ -4750,7 +4811,7 @@ FUN(Buffer_readBytesInto)(JNIEnv *env, jobject self, jint jat, jobject jbs, jint
 	jsize len = (jsize) jlen;
 	jsize bslen = 0;
 
-	if (!ctx) return -1;
+	if (!ctx || !buf) return -1;
 	if (jat < 0) { jni_throw_oob(env, "at is negative"); return -1; }
 	if (!jbs) { jni_throw_arg(env, "buffer must not be null"); return -1; }
 	if (joff < 0) { jni_throw_oob(env, "offset is negative"); return -1; }
@@ -4779,7 +4840,7 @@ FUN(Buffer_writeByte)(JNIEnv *env, jobject self, jbyte b)
 	fz_context *ctx = get_context(env);
 	fz_buffer *buf = from_Buffer(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !buf) return;
 
 	fz_try(ctx)
 		fz_write_buffer_byte(ctx, buf, b);
@@ -4795,7 +4856,7 @@ FUN(Buffer_writeBytes)(JNIEnv *env, jobject self, jobject jbs)
 	jsize len = 0;
 	jbyte *bs = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !buf) return;
 	if (!jbs) { jni_throw_arg(env, "buffer must not be null"); return; }
 
 	len = (*env)->GetArrayLength(env, jbs);
@@ -4820,7 +4881,7 @@ FUN(Buffer_writeBytesFrom)(JNIEnv *env, jobject self, jobject jbs, jint joff, ji
 	jsize len = (jsize) jlen;
 	jsize bslen = 0;
 
-	if (!ctx) return;
+	if (!ctx || !buf) return;
 	if (!jbs) { jni_throw_arg(env, "buffer must not be null"); return; }
 
 	bslen = (*env)->GetArrayLength(env, jbs);
@@ -4859,7 +4920,7 @@ FUN(Buffer_writeBuffer)(JNIEnv *env, jobject self, jobject jbuf)
 	fz_buffer *buf = from_Buffer(env, self);
 	fz_buffer *cat = from_Buffer(env, jbuf);
 
-	if (!ctx) return;
+	if (!ctx || !buf) return;
 	if (!cat) { jni_throw_arg(env, "buffer must not be null"); return; }
 
 	fz_try(ctx)
@@ -4874,7 +4935,7 @@ FUN(Buffer_writeRune)(JNIEnv *env, jobject self, jint rune)
 	fz_context *ctx = get_context(env);
 	fz_buffer *buf = from_Buffer(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !buf) return;
 
 	fz_try(ctx)
 		fz_write_buffer_rune(ctx, buf, rune);
@@ -4889,7 +4950,7 @@ FUN(Buffer_writeLine)(JNIEnv *env, jobject self, jstring jline)
 	fz_buffer *buf = from_Buffer(env, self);
 	const char *line = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !buf) return;
 	if (!jline) { jni_throw_arg(env, "line must not be null"); return; }
 
 	line = (*env)->GetStringUTFChars(env, jline, NULL);
@@ -4914,7 +4975,7 @@ FUN(Buffer_writeLines)(JNIEnv *env, jobject self, jobject jlines)
 	int i = 0;
 	jsize len = 0;
 
-	if (!ctx) return;
+	if (!ctx || !buf) return;
 	if (!jlines) { jni_throw_arg(env, "lines must not be null"); return; }
 
 	len = (*env)->GetArrayLength(env, jlines);
@@ -4954,7 +5015,7 @@ FUN(Buffer_save)(JNIEnv *env, jobject self, jstring jfilename)
 	fz_buffer *buf = from_Buffer(env, self);
 	const char *filename = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !buf) return;
 	if (jfilename)
 	{
 		filename = (*env)->GetStringUTFChars(env, jfilename, NULL);
@@ -4978,7 +5039,7 @@ FUN(DocumentWriter_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_document_writer *wri = from_DocumentWriter(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !wri) return;
 
 	fz_drop_document_writer(ctx, wri);
 }
@@ -4992,7 +5053,7 @@ FUN(DocumentWriter_newNativeDocumentWriter)(JNIEnv *env, jobject self, jstring j
 	const char *format = NULL;
 	const char *options = NULL;
 
-	if (!ctx) return 0;
+	if (!ctx || !wri) return 0;
 	if (!jfilename) { jni_throw_arg(env, "filename must not be null"); return 0; }
 
 	filename = (*env)->GetStringUTFChars(env, jfilename, NULL);
@@ -5046,7 +5107,7 @@ FUN(DocumentWriter_beginPage)(JNIEnv *env, jobject self, jobject jmediabox)
 	fz_rect mediabox = from_Rect(env, jmediabox);
 	fz_device *device = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !wri) return NULL;
 
 	fz_try(ctx)
 		device = fz_begin_page(ctx, wri, &mediabox);
@@ -5066,7 +5127,7 @@ FUN(DocumentWriter_endPage)(JNIEnv *env, jobject self, jobject jdev)
 	fz_document_writer *wri = from_DocumentWriter(env, self);
 	fz_device *device = from_Device(env, jdev);
 
-	if (!ctx) return;
+	if (!ctx || !wri) return;
 	if (!device) { jni_throw_arg(env, "device must not be null"); return; }
 
 	fz_try(ctx)
@@ -5081,7 +5142,7 @@ FUN(DocumentWriter_close)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_document_writer *wri = from_DocumentWriter(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !wri) return;
 
 	fz_try(ctx)
 		fz_close_document_writer(ctx, wri);
@@ -5097,7 +5158,7 @@ FUN(StructuredText_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_stext_page *text = from_StructuredText(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !text) return;
 
 	fz_drop_stext_page(ctx, text);
 }
@@ -5111,7 +5172,7 @@ FUN(StructuredText_search)(JNIEnv *env, jobject self, jstring jneedle)
 	const char *needle = NULL;
 	int n = 0;
 
-	if (!ctx) return NULL;
+	if (!ctx || !text) return NULL;
 	if (!jneedle) { jni_throw_arg(env, "needle must not be null"); return NULL; }
 
 	needle = (*env)->GetStringUTFChars(env, jneedle, NULL);
@@ -5139,7 +5200,7 @@ FUN(StructuredText_highlight)(JNIEnv *env, jobject self, jobject jrect)
 	fz_rect hits[256];
 	int n = 0;
 
-	if (!ctx) return NULL;
+	if (!ctx || !text) return NULL;
 
 	fz_try(ctx)
 		n = fz_highlight_selection(ctx, text, rect, hits, nelem(hits));
@@ -5161,7 +5222,7 @@ FUN(StructuredText_copy)(JNIEnv *env, jobject self, jobject jrect)
 	jobject jstring = NULL;
 	char *s = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !text) return NULL;
 
 	fz_var(s);
 
@@ -5209,7 +5270,7 @@ FUN(StructuredText_getBlocks)(JNIEnv *env, jobject self)
 	fz_rect bbox;
 	fz_stext_char *ch = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !text) return NULL;
 
 	//  create block array
 	barr = (*env)->NewObjectArray(env, text->len, cls_TextBlock, NULL);
@@ -5353,7 +5414,7 @@ FUN(PDFDocument_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	pdf_document *pdf = from_PDFDocument(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !pdf) return;
 
 	fz_drop_document(ctx, (fz_document *) pdf);
 }
@@ -5365,7 +5426,7 @@ FUN(PDFDocument_countObjects)(JNIEnv *env, jobject self)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	int count = 0;
 
-	if (!ctx) return 0;
+	if (!ctx || !pdf) return 0;
 
 	fz_try(ctx)
 		count = pdf_xref_len(ctx, pdf);
@@ -5385,7 +5446,7 @@ FUN(PDFDocument_newNull)(JNIEnv *env, jobject self)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_obj *obj = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	fz_try(ctx)
 		obj = pdf_new_null(ctx, pdf);
@@ -5405,7 +5466,7 @@ FUN(PDFDocument_newBoolean)(JNIEnv *env, jobject self, jboolean b)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_obj *obj = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	fz_try(ctx)
 		obj = pdf_new_bool(ctx, pdf, b);
@@ -5425,7 +5486,7 @@ FUN(PDFDocument_newInteger)(JNIEnv *env, jobject self, jint i)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_obj *obj = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	fz_try(ctx)
 		obj = pdf_new_int(ctx, pdf, i);
@@ -5445,7 +5506,7 @@ FUN(PDFDocument_newReal)(JNIEnv *env, jobject self, jfloat f)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_obj *obj = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	fz_try(ctx)
 		obj = pdf_new_real(ctx, pdf, f);
@@ -5466,7 +5527,7 @@ FUN(PDFDocument_newString)(JNIEnv *env, jobject self, jstring jstring)
 	pdf_obj *obj = NULL;
 	const char *s = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (!jstring) { jni_throw_arg(env, "string must not be null"); return NULL; }
 
 	s = (*env)->GetStringUTFChars(env, jstring, NULL);
@@ -5493,7 +5554,7 @@ FUN(PDFDocument_newName)(JNIEnv *env, jobject self, jstring jname)
 	pdf_obj *obj = NULL;
 	const char *name = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (!jname) { jni_throw_arg(env, "name must not be null"); return NULL; }
 
 	name = (*env)->GetStringUTFChars(env, jname, NULL);
@@ -5519,7 +5580,7 @@ FUN(PDFDocument_newIndirect)(JNIEnv *env, jobject self, jint num, jint gen)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_obj *obj = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	fz_try(ctx)
 		obj = pdf_new_indirect(ctx, pdf, num, gen);
@@ -5539,7 +5600,7 @@ FUN(PDFDocument_newArray)(JNIEnv *env, jobject self)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_obj *obj = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	fz_try(ctx)
 		obj = pdf_new_array(ctx, pdf, 0);
@@ -5559,7 +5620,7 @@ FUN(PDFDocument_newDictionary)(JNIEnv *env, jobject self)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_obj *obj = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	fz_try(ctx)
 		obj = pdf_new_dict(ctx, pdf, 0);
@@ -5578,7 +5639,7 @@ FUN(PDFDocument_toDocument)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	pdf_document *pdf = from_PDFDocument(env, self);
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	return to_Document_safe(ctx, env, (fz_document *) pdf);
 }
@@ -5590,7 +5651,7 @@ FUN(PDFDocument_countPages)(JNIEnv *env, jobject self)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	int count = 0;
 
-	if (!ctx) return 0;
+	if (!ctx || !pdf) return 0;
 
 	fz_try(ctx)
 		count = pdf_count_pages(ctx, pdf);
@@ -5611,7 +5672,7 @@ FUN(PDFDocument_findPage)(JNIEnv *env, jobject self, jint jat)
 	size_t at = (size_t) jat;
 	pdf_obj *obj = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (jat < 0 || jat >= pdf_count_pages(ctx, pdf)) { jni_throw_oob(env, "at is not a valid page"); return NULL; }
 
 	fz_try(ctx)
@@ -5632,7 +5693,7 @@ FUN(PDFDocument_getTrailer)(JNIEnv *env, jobject self)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_obj *obj = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	fz_try(ctx)
 		obj = pdf_trailer(ctx, pdf);
@@ -5652,7 +5713,7 @@ FUN(PDFDocument_addObject)(JNIEnv *env, jobject self, jobject jobj)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_obj *obj = from_PDFObject(env, jobj);
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (!jobj) { jni_throw_arg(env, "object must not be null"); return NULL; }
 
 	fz_try(ctx)
@@ -5673,7 +5734,7 @@ FUN(PDFDocument_createObject)(JNIEnv *env, jobject self)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_obj *ind = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	fz_try(ctx)
 		ind = pdf_new_indirect(ctx, pdf, pdf_create_object(ctx, pdf), 0);
@@ -5692,7 +5753,7 @@ FUN(PDFDocument_deleteObject)(JNIEnv *env, jobject self, jint num)
 	fz_context *ctx = get_context(env);
 	pdf_document *pdf = from_PDFDocument(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !pdf) return;
 
 	fz_try(ctx)
 		pdf_delete_object(ctx, pdf, num);
@@ -5707,7 +5768,7 @@ FUN(PDFDocument_newPDFGraftMap)(JNIEnv *env, jobject self)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	pdf_graft_map *map = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 
 	fz_try(ctx)
 		map = pdf_new_graft_map(ctx, pdf);
@@ -5729,7 +5790,7 @@ FUN(PDFDocument_graftObject)(JNIEnv *env, jobject self, jobject jsrc, jobject jo
 	pdf_obj *obj = from_PDFObject(env, jobj);
 	pdf_graft_map *map = from_PDFGraftMap(env, jmap);
 
-	if (!ctx) return NULL;
+	if (!ctx || !dst) return NULL;
 	if (!src) { jni_throw_arg(env, "source must not be null"); return NULL; }
 
 	fz_try(ctx)
@@ -5751,7 +5812,7 @@ FUN(PDFDocument_addStreamBuffer)(JNIEnv *env, jobject self, jobject jbuf)
 	fz_buffer *buf = from_Buffer(env, jbuf);
 	pdf_obj *ind = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (!jbuf) { jni_throw_arg(env, "buffer must not be null"); return NULL; }
 
 	fz_try(ctx)
@@ -5775,7 +5836,7 @@ FUN(PDFDocument_addStreamString)(JNIEnv *env, jobject self, jstring jbuf)
 	unsigned char *data = NULL;
 	pdf_obj *ind = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (!jbuf) { jni_throw_arg(env, "buffer must not be null"); return NULL; }
 
 	sbuf = (*env)->GetStringUTFChars(env, jbuf, NULL);
@@ -5819,7 +5880,7 @@ FUN(PDFDocument_addPageBuffer)(JNIEnv *env, jobject self, jobject jmediabox, jin
 	fz_buffer *contents = from_Buffer(env, jcontents);
 	pdf_obj *ind = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (!resources) { jni_throw_arg(env, "resources must not be null"); return NULL; }
 	if (!contents) { jni_throw_arg(env, "contents must not be null"); return NULL; }
 
@@ -5846,7 +5907,7 @@ FUN(PDFDocument_addPageString)(JNIEnv *env, jobject self, jobject jmediabox, jin
 	unsigned char *data = NULL;
 	pdf_obj *ind = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (!resources) { jni_throw_arg(env, "resources must not be null"); return NULL; }
 	if (!contents) { jni_throw_arg(env, "contents must not be null"); return NULL; }
 
@@ -5887,7 +5948,7 @@ FUN(PDFDocument_insertPage)(JNIEnv *env, jobject self, jint jat, jobject jpage)
 	size_t at = (size_t) jat;
 	pdf_obj *page = from_PDFObject(env, jpage);
 
-	if (!ctx) return;
+	if (!ctx || !pdf) return;
 	if (jat < 0 || jat >= pdf_count_pages(ctx, pdf)) { jni_throw_oob(env, "at is not a valid page"); return; }
 	if (!page) { jni_throw_arg(env, "page must not be null"); return; }
 
@@ -5904,7 +5965,7 @@ FUN(PDFDocument_deletePage)(JNIEnv *env, jobject self, jint jat)
 	pdf_document *pdf = from_PDFDocument(env, self);
 	size_t at = (size_t) jat;
 
-	if (!ctx) return;
+	if (!ctx || !pdf) return;
 	if (jat < 0 || jat >= pdf_count_pages(ctx, pdf)) { jni_throw_oob(env, "at is not a valid page"); return; }
 
 	fz_try(ctx)
@@ -5921,7 +5982,7 @@ FUN(PDFDocument_addImage)(JNIEnv *env, jobject self, jobject jimage)
 	fz_image *image = from_Image(env, jimage);
 	pdf_obj *ind = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (!image) { jni_throw_arg(env, "image must not be null"); return NULL; }
 
 	fz_try(ctx)
@@ -5943,7 +6004,7 @@ FUN(PDFDocument_addFont)(JNIEnv *env, jobject self, jobject jfont)
 	fz_font *font = from_Font(env, jfont);
 	pdf_obj *ind = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (!font) { jni_throw_arg(env, "font must not be null"); return NULL; }
 
 	fz_try(ctx)
@@ -5965,7 +6026,7 @@ FUN(PDFDocument_addSimpleFont)(JNIEnv *env, jobject self, jobject jfont)
 	fz_font *font = from_Font(env, jfont);
 	pdf_obj *ind = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !pdf) return NULL;
 	if (!font) { jni_throw_arg(env, "font must not be null"); return NULL; }
 
 	fz_try(ctx)
@@ -5984,7 +6045,7 @@ FUN(PDFDocument_hasUnsavedChanges)(JNIEnv *env, jobject self)
 {
 	fz_context *ctx = get_context(env);
 	pdf_document *pdf = from_PDFDocument(env, self);
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !pdf) return JNI_FALSE;
 	return pdf_has_unsaved_changes(ctx, pdf) ? JNI_TRUE : JNI_FALSE;
 }
 
@@ -5993,7 +6054,7 @@ FUN(PDFDocument_canBeSavedIncrementally)(JNIEnv *env, jobject self)
 {
 	fz_context *ctx = get_context(env);
 	pdf_document *pdf = from_PDFDocument(env, self);
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !pdf) return JNI_FALSE;
 	return pdf_can_be_saved_incrementally(ctx, pdf) ? JNI_TRUE : JNI_FALSE;
 }
 
@@ -6007,7 +6068,7 @@ FUN(PDFDocument_save)(JNIEnv *env, jobject self, jstring jfilename, jstring jopt
 	pdf_write_options pwo;
 	int errors = 0;
 
-	if (!ctx) return 0;
+	if (!ctx || !pdf) return 0;
 	if (!jfilename) { jni_throw_arg(env, "filename must not be null"); return 0; }
 
 	filename = (*env)->GetStringUTFChars(env, jfilename, NULL);
@@ -6049,7 +6110,7 @@ FUN(PDFObject_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	pdf_obj *obj = from_PDFObject(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !obj) return;
 
 	pdf_drop_obj(ctx, obj);
 }
@@ -6061,7 +6122,7 @@ FUN(PDFObject_toIndirect)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int num = 0;
 
-	if (!ctx) return 0;
+	if (!ctx || !obj) return 0;
 
 	fz_try(ctx)
 		num = pdf_to_num(ctx, obj);
@@ -6081,7 +6142,7 @@ FUN(PDFObject_isIndirect)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_indirect(ctx, obj);
@@ -6101,7 +6162,7 @@ FUN(PDFObject_isNull)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_null(ctx, obj);
@@ -6121,7 +6182,7 @@ FUN(PDFObject_isBoolean)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_bool(ctx, obj);
@@ -6141,7 +6202,7 @@ FUN(PDFObject_isInteger)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_int(ctx, obj);
@@ -6161,7 +6222,7 @@ FUN(PDFObject_isReal)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_real(ctx, obj);
@@ -6181,7 +6242,7 @@ FUN(PDFObject_isNumber)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_number(ctx, obj);
@@ -6201,7 +6262,7 @@ FUN(PDFObject_isString)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_string(ctx, obj);
@@ -6221,7 +6282,7 @@ FUN(PDFObject_isName)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_name(ctx, obj);
@@ -6241,7 +6302,7 @@ FUN(PDFObject_isArray)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_array(ctx, obj);
@@ -6261,7 +6322,7 @@ FUN(PDFObject_isDictionary)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_dict(ctx, obj);
@@ -6281,7 +6342,7 @@ FUN(PDFObject_isStream)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_is_stream(ctx, obj);
@@ -6302,7 +6363,7 @@ FUN(PDFObject_readStream)(JNIEnv *env, jobject self)
 	fz_buffer *buf = NULL;
 	jbyteArray arr = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !obj) return NULL;
 
 	fz_var(buf);
 
@@ -6337,7 +6398,7 @@ FUN(PDFObject_readRawStream)(JNIEnv *env, jobject self)
 	fz_buffer *buf = NULL;
 	jbyteArray arr = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !obj) return NULL;
 
 	fz_var(buf);
 
@@ -6372,7 +6433,7 @@ FUN(PDFObject_writeObject)(JNIEnv *env, jobject self, jobject jobj)
 	pdf_document *pdf = pdf_get_bound_document(ctx, ref);
 	pdf_obj *obj = from_PDFObject(env, jobj);
 
-	if (!ctx) return;
+	if (!ctx || !obj) return;
 	if (!pdf) { jni_throw_arg(env, "object not bound to document"); return; }
 	if (!obj) { jni_throw_arg(env, "object must not be null"); return; }
 
@@ -6390,7 +6451,7 @@ FUN(PDFObject_writeStreamBuffer)(JNIEnv *env, jobject self, jobject jbuf)
 	pdf_document *pdf = pdf_get_bound_document(ctx, obj);
 	fz_buffer *buf = from_Buffer(env, jbuf);
 
-	if (!ctx) return;
+	if (!ctx || !obj) return;
 	if (!pdf) { jni_throw_arg(env, "object not bound to document"); return; }
 	if (!buf) { jni_throw_arg(env, "buffer must not be null"); return; }
 
@@ -6410,7 +6471,7 @@ FUN(PDFObject_writeStreamString)(JNIEnv *env, jobject self, jstring jstr)
 	unsigned char *data = NULL;
 	fz_buffer *buf = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !obj) return;
 	if (!pdf) { jni_throw_arg(env, "object not bound to document"); return; }
 	if (!jstr) { jni_throw_arg(env, "string must not be null"); return; }
 
@@ -6447,7 +6508,7 @@ FUN(PDFObject_writeRawStreamBuffer)(JNIEnv *env, jobject self, jobject jbuf)
 	pdf_document *pdf = pdf_get_bound_document(ctx, obj);
 	fz_buffer *buf = from_Buffer(env, jbuf);
 
-	if (!ctx) return;
+	if (!ctx || !obj) return;
 	if (!pdf) { jni_throw_arg(env, "object not bound to document"); return; }
 	if (!buf) { jni_throw_arg(env, "buffer must not be null"); return; }
 
@@ -6467,7 +6528,7 @@ FUN(PDFObject_writeRawStreamString)(JNIEnv *env, jobject self, jstring jstr)
 	unsigned char *data = NULL;
 	fz_buffer *buf = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !obj) return;
 	if (!pdf) { jni_throw_arg(env, "object not bound to document"); return; }
 	if (!jstr) { jni_throw_arg(env, "string must not be null"); return; }
 
@@ -6504,7 +6565,7 @@ FUN(PDFObject_resolve)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	pdf_obj *ind = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !obj) return NULL;
 	if (!obj) { jni_throw_arg(env, "object must not be null"); return NULL; }
 
 	fz_try(ctx)
@@ -6526,7 +6587,7 @@ FUN(PDFObject_getArray)(JNIEnv *env, jobject self, jint index)
 	pdf_obj *arr = from_PDFObject(env, self);
 	pdf_obj *val = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !arr) return NULL;
 
 	fz_try(ctx)
 		val = pdf_array_get(ctx, arr, index);
@@ -6547,7 +6608,7 @@ FUN(PDFObject_getDictionary)(JNIEnv *env, jobject self, jstring jname)
 	const char *name = NULL;
 	pdf_obj *val = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !dict) return NULL;
 	if (jname)
 	{
 		name = (*env)->GetStringUTFChars(env, jname, NULL);
@@ -6575,7 +6636,7 @@ FUN(PDFObject_putArrayBoolean)(JNIEnv *env, jobject self, jint index, jboolean b
 	pdf_obj *arr = from_PDFObject(env, self);
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 
 	fz_try(ctx)
 	{
@@ -6596,7 +6657,7 @@ FUN(PDFObject_putArrayInteger)(JNIEnv *env, jobject self, jint index, jint i)
 	pdf_obj *arr = from_PDFObject(env, self);
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 
 	fz_try(ctx)
 	{
@@ -6617,7 +6678,7 @@ FUN(PDFObject_putArrayFloat)(JNIEnv *env, jobject self, jint index, jfloat f)
 	pdf_obj *arr = from_PDFObject(env, self);
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 
 	fz_try(ctx)
 	{
@@ -6639,7 +6700,7 @@ FUN(PDFObject_putArrayString)(JNIEnv *env, jobject self, jint index, jstring jst
 	const char *str = NULL;
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 	if (jstr)
 	{
 		str = (*env)->GetStringUTFChars(env, jstr, NULL);
@@ -6669,7 +6730,7 @@ FUN(PDFObject_putArrayPDFObject)(JNIEnv *env, jobject self, jint index, jobject
 	pdf_obj *arr = from_PDFObject(env, self);
 	pdf_obj *obj = from_PDFObject(env, jobj);
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 
 	fz_try(ctx)
 		pdf_array_put(ctx, arr, index, obj);
@@ -6686,7 +6747,7 @@ FUN(PDFObject_putDictionaryStringBoolean)(JNIEnv *env, jobject self, jstring jna
 	pdf_obj *key = NULL;
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 	if (jname)
 	{
 		name = (*env)->GetStringUTFChars(env, jname, NULL);
@@ -6720,7 +6781,7 @@ FUN(PDFObject_putDictionaryStringInteger)(JNIEnv *env, jobject self, jstring jna
 	pdf_obj *key = NULL;
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 	if (jname)
 	{
 		name = (*env)->GetStringUTFChars(env, jname, NULL);
@@ -6754,7 +6815,7 @@ FUN(PDFObject_putDictionaryStringFloat)(JNIEnv *env, jobject self, jstring jname
 	pdf_obj *key = NULL;
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 	if (jname)
 	{
 		name = (*env)->GetStringUTFChars(env, jname, NULL);
@@ -6790,7 +6851,7 @@ FUN(PDFObject_putDictionaryStringString)(JNIEnv *env, jobject self, jstring jnam
 	pdf_obj *key = NULL;
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 	if (jname)
 	{
 		name = (*env)->GetStringUTFChars(env, jname, NULL);
@@ -6835,7 +6896,7 @@ FUN(PDFObject_putDictionaryStringPDFObject)(JNIEnv *env, jobject self, jstring j
 	const char *name = NULL;
 	pdf_obj *key = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 	if (jname)
 	{
 		name = (*env)->GetStringUTFChars(env, jname, NULL);
@@ -6865,7 +6926,7 @@ FUN(PDFObject_putDictionaryPDFObjectBoolean)(JNIEnv *env, jobject self, jobject
 	pdf_obj *name = from_PDFObject(env, jname);
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 
 	fz_try(ctx)
 	{
@@ -6887,7 +6948,7 @@ FUN(PDFObject_putDictionaryPDFObjectInteger)(JNIEnv *env, jobject self, jobject
 	pdf_obj *name = from_PDFObject(env, jname);
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 
 	fz_try(ctx)
 	{
@@ -6909,7 +6970,7 @@ FUN(PDFObject_putDictionaryPDFObjectFloat)(JNIEnv *env, jobject self, jobject jn
 	pdf_obj *name = from_PDFObject(env, jname);
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 
 	fz_try(ctx)
 	{
@@ -6932,7 +6993,7 @@ FUN(PDFObject_putDictionaryPDFObjectString)(JNIEnv *env, jobject self, jobject j
 	const char *str = NULL;
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 	if (jstr)
 	{
 		str = (*env)->GetStringUTFChars(env, jstr, NULL);
@@ -6963,7 +7024,7 @@ FUN(PDFObject_putDictionaryPDFObjectPDFObject)(JNIEnv *env, jobject self, jobjec
 	pdf_obj *name = from_PDFObject(env, jname);
 	pdf_obj *obj = from_PDFObject(env, jobj);
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 
 	fz_try(ctx)
 		pdf_dict_put(ctx, dict, name, obj);
@@ -6977,7 +7038,7 @@ FUN(PDFObject_deleteArray)(JNIEnv *env, jobject self, jint index)
 	fz_context *ctx = get_context(env);
 	pdf_obj *arr = from_PDFObject(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 
 	fz_try(ctx)
 		pdf_array_delete(ctx, arr, index);
@@ -6993,7 +7054,7 @@ FUN(PDFObject_deleteDictionaryString)(JNIEnv *env, jobject self, jstring jname)
 	const char *name = NULL;
 	pdf_obj *val = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 	if (jname)
 	{
 		name = (*env)->GetStringUTFChars(env, jname, NULL);
@@ -7023,7 +7084,7 @@ FUN(PDFObject_deleteDictionaryPDFObject)(JNIEnv *env, jobject self, jobject jnam
 	pdf_obj *dict = from_PDFObject(env, self);
 	pdf_obj *name = from_PDFObject(env, jname);
 
-	if (!ctx) return;
+	if (!ctx || !dict) return;
 
 	fz_try(ctx)
 		pdf_dict_del(ctx, dict, name);
@@ -7038,7 +7099,7 @@ FUN(PDFObject_toBoolean)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int b = 0;
 
-	if (!ctx) return JNI_FALSE;
+	if (!ctx || !obj) return JNI_FALSE;
 
 	fz_try(ctx)
 		b = pdf_to_bool(ctx, obj);
@@ -7058,7 +7119,7 @@ FUN(PDFObject_toInteger)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	int i = 0;
 
-	if (!ctx) return 0;
+	if (!ctx || !obj) return 0;
 
 	fz_try(ctx)
 		i = pdf_to_int(ctx, obj);
@@ -7078,7 +7139,7 @@ FUN(PDFObject_toFloat)(JNIEnv *env, jobject self)
 	pdf_obj *obj = from_PDFObject(env, self);
 	float f = 0;
 
-	if (!ctx) return 0;
+	if (!ctx || !obj) return 0;
 
 	fz_try(ctx)
 		f = pdf_to_real(ctx, obj);
@@ -7100,7 +7161,7 @@ FUN(PDFObject_toByteString)(JNIEnv *env, jobject self)
 	jobject jbs = NULL;
 	jbyte *bs = NULL;
 
-	if (!ctx) return NULL;
+	if (!ctx || !obj) return NULL;
 
 	fz_try(ctx)
 		if (pdf_is_name(ctx, obj))
@@ -7132,7 +7193,7 @@ FUN(PDFObject_size)(JNIEnv *env, jobject self)
 	pdf_obj *arr = from_PDFObject(env, self);
 	int len;
 
-	if (!ctx) return 0;
+	if (!ctx || !arr) return 0;
 
 	fz_try(ctx)
 		len = pdf_array_len(ctx, arr);
@@ -7152,7 +7213,7 @@ FUN(PDFObject_pushBoolean)(JNIEnv *env, jobject self, jboolean b)
 	pdf_obj *arr = from_PDFObject(env, self);
 	pdf_obj *item = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 
 	fz_try(ctx)
 	{
@@ -7173,7 +7234,7 @@ FUN(PDFObject_pushInteger)(JNIEnv *env, jobject self, jint i)
 	pdf_obj *arr = from_PDFObject(env, self);
 	pdf_obj *item = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 
 	fz_try(ctx)
 	{
@@ -7194,7 +7255,7 @@ FUN(PDFObject_pushFloat)(JNIEnv *env, jobject self, jfloat f)
 	pdf_obj *arr = from_PDFObject(env, self);
 	pdf_obj *item = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 
 	fz_try(ctx)
 	{
@@ -7216,7 +7277,7 @@ FUN(PDFObject_pushString)(JNIEnv *env, jobject self, jstring jstr)
 	const char *str = NULL;
 	pdf_obj *item = NULL;
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 	if (jstr)
 	{
 		str = (*env)->GetStringUTFChars(env, jstr, NULL);
@@ -7246,7 +7307,7 @@ FUN(PDFObject_pushPDFObject)(JNIEnv *env, jobject self, jobject jitem)
 	pdf_obj *arr = from_PDFObject(env, self);
 	pdf_obj *item = from_PDFObject(env, jitem);
 
-	if (!ctx) return;
+	if (!ctx || !arr) return;
 
 	fz_try(ctx)
 		pdf_array_push(ctx, arr, item);
@@ -7265,7 +7326,7 @@ FUN(PDFObject_toString)(JNIEnv *env, jobject self, jboolean tight)
 	char *s = NULL;
 	int n = 0;
 
-	if (!ctx) return NULL;
+	if (!ctx || !obj) return NULL;
 
 	fz_var(s);
 
@@ -7295,7 +7356,7 @@ FUN(Shade_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	fz_shade *shd = from_Shade(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !shd) return;
 
 	fz_drop_shade(ctx, shd);
 }
@@ -7308,7 +7369,7 @@ FUN(PDFGraftMap_finalize)(JNIEnv *env, jobject self)
 	fz_context *ctx = get_context(env);
 	pdf_graft_map *map = from_PDFGraftMap(env, self);
 
-	if (!ctx) return;
+	if (!ctx || !map) return;
 
 	pdf_drop_graft_map(ctx, map);
 }