It could be that since UE4 is crashing before building the lights there is indeed no Build folder. Try to remove everything except Config, Content, Source if any and the .uproject file. Make sure you make a backup copy first.
It could be that since UE4 is crashing before building the lights there is indeed no Build folder. Try to remove everything except Config, Content, Source if any and the .uproject file. Make sure you make a backup copy first.