An update from 3.0.1 to 3.0.3 broke my application, because you've added a non-empty-list-assertion in your StoreAddEvent.
That's my use case: I'm adding elements to my table(s) using getStore().addAll(listOfElements). The number of the elements is unknown. Checking if it's 0 before each add() call seems to be a bad idea for me (but the only workaround for now). Especially because it had worked before.
I understand your assertion (there should be no StoreAddEvent, if the store remains unchanged). But it should not be our concern, since it's GXT which fires a StoreAddEvent, even though there are no elements.