Get an existing state object from a controlID.
This will return a recycled state object that is unique for controlID
.
If the state object has not been created by calling GetStateObject then it
cannot be accessed using QueryStateObject. A call into QueryStateObject
with the state object not created is invalid. A null may be returned, but is not
guaranteed. An exception may happen instead.
Additional resources: GUIUtility.GetStateObject.