As title , error screenshot - https://imgur.com/a/9ljOC1Q

Mods used

SE 0.5.55 + K2 1.1.3 (along with the dependencies), K2 more locomotives 11.0.0, Electric train 1.1.2, Rate Calculator 2.2.0 and some other minor QOL

The error occured when switching from normal locomotive to electric .

Same problem as https://mods.factorio.com/mod/Train_Control_Signals/discussion/60a2bda2b71b52dc6815ddcc

If you don’t want to wait for Klonan to fix the mod, you can fix it yourself by unzipping the mod, editing Train_Control_Signals_1.0.4/script/train_control_signals.lua and adding this in line 17 (after fuel_inventory.sort_and_merge()):

  if #fuel_inventory == 0 then
    return false
  end