Attaching a Cargo Wagon to one of these locomotives kicks you back to the main menu with this error:
Error while running event FollowerLocomotive::on_tick (ID 0)
FollowerLocomotive/control.lua:101: attempt to index field '?' (a nil value)
It's consistent, too. Sits there just fine until I add a cargo wagon, after which this error pops up about a second later 100% of the time.
