avcodec_alloc_frame: dont zero the whole struct twice

cleaning it up is already done in avcodec_get_frame_defaults()

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/utils.c

@@ -720,11 +720,12 @@ void avcodec_get_frame_defaults(AVFrame *frame)
 
 AVFrame *avcodec_alloc_frame(void)
 {
-    AVFrame *frame = av_mallocz(sizeof(AVFrame));
+    AVFrame *frame = av_malloc(sizeof(AVFrame));
 
     if (frame == NULL)
         return NULL;
 
+    frame->extended_data = NULL;
     avcodec_get_frame_defaults(frame);
 
     return frame;