We had a error while playing, the mod also didnt work for ous
Error while running event BeltUpgrader::on_nth_tick(180) BeltUpgrader/control.lua:179: attempt to perform arithmetic on field '?' (a nil value)
stack traceback: BeltUpgrader/control.lua:179: in function 'upgrade' BeltUpgrader/control.lua:77: in function <BeltUpgrader/control.lua:61>
