Fix potential NPE when saving/deleting Autofill profile.

As the callback to display a toast confirmation to the user is
asynchronous there's a chance that the Fragment might be detached
when the callback is invoked. Guard against the potential NPE in
this case.

Bug: 5142413
Change-Id: Ic331e1ef3b738c5f2415b028da42c81f8f5e84d2
1 file changed