Segfault due to desktop widget deletion

Pyside will delete the widget returned by QApplication.desktop() if the .parent() method of the returned desktop widget has been called. Occurs because QApplication.desktop() sets the pyside parent to the application due to the set_qapp_parent_for_orphan injected code, but the .parent() call sets it to None because the C++ returned parent is NULL. This causes the hasOwnership C++ attribute of the wrapper to be set to true and a C++ delete call made when the ref count on the wrapper goes to 0.

Other methods that use set_qapp_parent_for_orphan may have similar bugs.