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 get_sidx_size(AVFormatContext *s)
{
    int ret;
    AVIOContext *buf;
    MOVMuxContext *mov = s->priv_data;

    if ((ret = ffio_open_null_buf(&buf)) < 0)
        return ret;
    mov_write_sidx_tags(buf, mov, -1, 0);
    return ffio_close_null_buf(buf);
}

static int get_sidx_size(AVFormatContext *s)
{
    int ret;
    AVIOContext *buf;
    MOVMuxContext *mov = s->priv_data;

    if ((ret = ffio_open_null_buf(&buf)) < 0)
        return ret;
    mov_write_sidx_tags(buf, mov, -1, 0);
    return ffio_close_null_buf(buf);
}
