The mod Multiple Unit Train Control (0.4.9) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event MultipleUnitTrainControl::on_init()
Error when running interface function realistic_electric_trains.get_locomotive_fuel: Realistic_Electric_Trains_Fork/logic/remotes.lua:28: attempt to index field 'electric_loco_registry' (a nil value)
stack traceback:
Realistic_Electric_Trains_Fork/logic/remotes.lua:28: in function <Realistic_Electric_Trains_Fork/logic/remotes.lua:27>
stack traceback:
[C]: in function 'call'
MultipleUnitTrainControl/control.lua:91: in function 'InitEntityMaps'
MultipleUnitTrainControl/control.lua:701: in function <MultipleUnitTrainControl/control.lua:695>

Please post this for the author of Realistic Electric Train Fork as well. It could be something they changed in the previously working interface function.

Will do

I found the issue (needed to added the forked mod to my dependency list) and uploaded the fix just now.

Thank you!