ffmpeg: Fix bsf corrupting merged side data

Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

ffmpeg.c

@@ -790,6 +790,7 @@ static void output_packet(OutputFile *of, AVPacket *pkt, OutputStream *ost)
     if (ost->nb_bitstream_filters) {
         int idx;
 
+        av_packet_split_side_data(pkt);
         ret = av_bsf_send_packet(ost->bsf_ctx[0], pkt);
         if (ret < 0)
             goto finish;