In a light switch, the neutral and ground are the same thing!
If you open your house pannel, you will see that all the neutral wires collect to a bus bar, as also do the ground wires connect to a similar bus bar. The two bus bars are connected!
The object of having the ground wire in addition to the neutral, is so that when a man works on the electrical switch, outlet, or what have you...........
If you disconnect the neutral wire, and didn't have a separate ground wire, there is the possibility, that you could become the ground, sustaining a possibly fatal shock!