Fixed iOS6 crash due to view being associated with multiple parent views

This should fix the crash in iOS 6 that happens when a NibLoadedView is deallocated. This happens because iOS6 still returns the old container view as it's superview after it has been added to it's new parent. 

This usually either crashes in [NSISEngine removeConstraintWithMarker:] on a device  or "getpid" on the simulator.