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 uint16_t language_code(const char *str)
{
    return (((str[0] - 0x60) & 0x1F) << 10) +
           (((str[1] - 0x60) & 0x1F) <<  5) +
           (( str[2] - 0x60) & 0x1F);
}

static uint16_t language_code(const char *str)
{
    return (((str[0] - 0x60) & 0x1F) << 10) +
           (((str[1] - 0x60) & 0x1F) <<  5) +
           (( str[2] - 0x60) & 0x1F);
}
