[REG: 5->6] Weird dock widget issue with recreated QApplication

To reproduce:

• run attached example
• double click on the item shown on list view
• dock the dock widget
• try to undock the dock widget

For some reason the dock seems to not react. If the QLineEdit is removed or the text isn't set in clicked(), it works. Also it works if the dialog is closed through alt+f4, or if close() event is delayed to happen after release event has been processed.