Null pointer check / CID26.

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@13488 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavformat/yuv4mpeg.c

@@ -322,6 +322,8 @@ static int yuv4_read_header(AVFormatContext *s, AVFormatParameters *ap)
     }
 
     st = av_new_stream(s, 0);
+    if(!st)
+        return -1;
     st->codec->width = width;
     st->codec->height = height;
     av_reduce(&raten, &rated, raten, rated, (1UL<<31)-1);