movenc: Include empty tracks in iods when writing fragmented mp4

When writing fragmented streams with an empty initial moov,
we won't have any samples in any tracks when writing the
moov atom, thus trust that any tracks that are added actually
will be present.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/movenc.c

@@ -1809,7 +1809,7 @@ static int mov_write_iods_tag(AVIOContext *pb, MOVMuxContext *mov)
     int audio_profile = mov->iods_audio_profile;
     int video_profile = mov->iods_video_profile;
     for (i = 0; i < mov->nb_streams; i++) {
-        if (mov->tracks[i].entry > 0) {
+        if (mov->tracks[i].entry > 0 || mov->flags & FF_MOV_FLAG_EMPTY_MOOV) {
             has_audio |= mov->tracks[i].enc->codec_type == AVMEDIA_TYPE_AUDIO;
             has_video |= mov->tracks[i].enc->codec_type == AVMEDIA_TYPE_VIDEO;
         }