Im making an aiming feature but i cant get it to work?

PlayerGui.LocalScript:31: invalid argument #2 (Vector3 expected, got nil)

I keep getting this error and it has to do something with this

	*aimcf 

how do I fix this?

			* aimcf
	)
	
	if aiming then
		aimcf = aimcf:Lerp(WeaponData.AimCFrame,0.2) --Goal CFrame (lower the number, lower the speed is)
	else
		aimcf = aimcf:Lerp(CFrame.new(), 0.1)