static int mov_write_smhd_tag(AVIOContext *pb)
{
    avio_wb32(pb, 16); /* size */
    ffio_wfourcc(pb, "smhd");
    avio_wb32(pb, 0); /* version & flags */
    avio_wb16(pb, 0); /* reserved (balance, normally = 0) */
    avio_wb16(pb, 0); /* reserved */
    return 16;
}

The product divides a value by zero.