10l (obmc_scratchpad not always initialize)

patch by (Gert Vervoort <gert.vervoort at hccnet dot nl>)

Originally committed as revision 3816 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/h264.c

@@ -2540,6 +2540,8 @@ static int alloc_tables(H264Context *h){
         }
     }
 
+    s->obmc_scratchpad = NULL;
+
     return 0;
 fail:
     free_tables(h);