Error: scripts/game/thing.lua:72: attempt to perform arithmetic on field 'health' (a nil value)
stack traceback:
	[string "boot.lua"]:777: in function '__sub'
	scripts/game/thing.lua:72: in function 'getDamage'
	scripts/game/thing.lua:42: in function 'onOverlap'
	scripts/game/bullet.lua:58: in function 'onOverlap'
	scripts/base/entity.lua:571: in function 'resolveCollision'
	scripts/base/scene.lua:389: in function 'resolveCollision'
	scripts/base/scene.lua:43: in function 'update'
	scripts/head/gamemanager.lua:45: in function 'update'
	scripts/head/statemanager.lua:10: in function 'update'
	main.lua:129: in function 'update'
	[string "boot.lua"]:612: in function <[string "boot.lua"]:594>
	[C]: in function 'xpcall'