sanity check whether dimensions are non-null

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@4634 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/imgresample.c

@@ -558,6 +558,9 @@ ImgReSampleContext *img_resample_full_init(int owidth, int oheight,
 {
     ImgReSampleContext *s;
 
+    if (!owidth || !oheight || !iwidth || !iheight)
+	return NULL;
+
     s = av_mallocz(sizeof(ImgReSampleContext));
     if (!s)
         return NULL;