Don't write an empty spdif header in spdif muxers write_header function before actual data starts.

Patch by Elupus.

Originally committed as revision 22814 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavformat/spdif.c

@@ -238,10 +238,6 @@ static int spdif_write_header(AVFormatContext *s)
         av_log(s, AV_LOG_ERROR, "codec not supported\n");
         return -1;
     }
-    put_le16(s->pb, 0);
-    put_le16(s->pb, 0);
-    put_le16(s->pb, 0);
-    put_le16(s->pb, 0);
     return 0;
 }