Zero the frame data on allocation for VB codec, e.g. the FATE sample seems to

rely on this.

Originally committed as revision 21394 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/vb.c

@@ -269,8 +269,8 @@ static av_cold int decode_init(AVCodecContext *avctx)
     c->avctx = avctx;
     avctx->pix_fmt = PIX_FMT_PAL8;
 
-    c->frame      = av_malloc( avctx->width * avctx->height);
-    c->prev_frame = av_malloc( avctx->width * avctx->height);
+    c->frame      = av_mallocz(avctx->width * avctx->height);
+    c->prev_frame = av_mallocz(avctx->width * avctx->height);
 
     memset(c->pal, 0, sizeof(c->pal));