Error:
Error while running event level::on_nth_tick(1)
__level__/control.lua:86: attempt to index global 'global' (a nil value)
stack traceback:
__level__/control.lua:86: in function <level/control.lua:85>
Repro:
1) Create new RailTester world
2) Save RailTester world
3) Load RailTester world
4) Crash with above error
