8e5840359f
by ensuring `KernelLight.lightgroup` is properly assigned in `device_update_light()`. The value is later retrieved via `lamp_lightgroup(kg, lamp)`. `light_manager->device_update()` is called after `background->device_update()`, so the background light group should already been assigned when `device_update_lights()` is called. Pull Request: https://projects.blender.org/blender/blender/pulls/120714