Set data_size to zero when DCA header parse failed

Patch by Limin Wang <lance('\\'>>1)lmwang>(0x24^'D')<gmail>('/' & 0xFE)<com>
Thread [PATCH] set data_size to zero if failed to parse dca header

Originally committed as revision 10423 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/dca.c

@@ -1151,6 +1151,7 @@ static int dca_decode_frame(AVCodecContext * avctx,
     init_get_bits(&s->gb, s->dca_buffer, s->dca_buffer_size * 8);
     if (dca_parse_frame_header(s) < 0) {
         //seems like the frame is corrupt, try with the next one
+        *data_size=0;
         return buf_size;
     }
     //set AVCodec values with parsed data