And, according to the docker inspect you posted,
"Binds": [
"/media/music:/media:rw",
"/mnt/user/appdata/binhex-airsonic-advanced:/config:rw"
],
You changed the host path of /mnt/user/music that you originally had to instead be /media/music (which doesn't exist on the host). You have the paths in the template correct in the first place.