Crash when cloning QGraphicsSceneEvent (not implemented)

When using QGraphicsSceneEvent in conjunction with QStateMachine, where
QStateMachine::WrappedEvent holds a cloned copy of an event (created by QEvent::clone()), crashes occur when accessing something that uses the d-ptr of the QGraphicsSceneEvent classes, fex QGraphicsSceneMouseEvent::buttons().

Steps to reproduce:

• Launch attached example
• Click within red frame
• observe crash