Everytime I build I get this error. It showed up after deleting all my lights and adding a few back.
Error === Lightmass crashed: ===Unhandled Exception: EXCEPTION_INT_DIVIDE_BY_ZERO
Fatal error: [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.5\Engine\Source\Programs\UnrealLightmass\Private\Lighting\LightingSystem.cpp] [Line: 1324]
Static lighting thread exception:
I had a similar error and it has been fixed by removing the add to viewport node from level blueprint.