avformat/movenc: Write version 2 of audio atom if channels is not known

The version 1 needs the channel count and would divide by 0
Fixes: division by 0
Fixes: fpe_movenc.c_1108_1.ogg
Fixes: fpe_movenc.c_1108_2.ogg
Fixes: fpe_movenc.c_1108_3.wav

Found-by: #CHEN HONGXU# <HCHEN017@e.ntu.edu.sg>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
static int mov_write_track_metadata(AVIOContext *pb, AVStream *st,
                                    const char *tag, const char *str)
{
    int64_t pos = avio_tell(pb);
    AVDictionaryEntry *t = av_dict_get(st->metadata, str, NULL, 0);
    if (!t || !utf8len(t->value))
        return 0;

    avio_wb32(pb, 0);   /* size */
    ffio_wfourcc(pb, tag); /* type */
    avio_write(pb, t->value, strlen(t->value)); /* UTF8 string value */
    return update_size(pb, pos);
}

static int mov_write_track_metadata(AVIOContext *pb, AVStream *st,
                                    const char *tag, const char *str)
{
    int64_t pos = avio_tell(pb);
    AVDictionaryEntry *t = av_dict_get(st->metadata, str, NULL, 0);
    if (!t || !utf8len(t->value))
        return 0;

    avio_wb32(pb, 0);   /* size */
    ffio_wfourcc(pb, tag); /* type */
    avio_write(pb, t->value, strlen(t->value)); /* UTF8 string value */
    return update_size(pb, pos);
}
