add defensive checks to LightSource to prevent server NRE
add defensive checks to LightSource to prevent server NRE

fomalsd/unitystation,krille90/unitystation,fomalsd/unitystation,fomalsd/unitystation,krille90/unitystation,Necromunger/unitystation,Necromunger/unitystation,fomalsd/unitystation,Necromunger/unitystation,Necromunger/unitystation,krille90/unitystation,Necromunger/unitystation,fomalsd/unitystation,fomalsd/unitystation,fomalsd/unitystation,Necromunger/unitystation