macOS: Closing application window while context menu is open leaves menu open

An application window can be closed using the close button from the titlebar on Mac even while context menu is shown. This is consistent with native macOS applications. However, the context menu remains open and visible (unless the application quits in response to the window closing, obviously).

Steps to reproduce:

• run the attached reproducer in QTBUG30522.zip, which turns off the QApplication::setQuitOnLastWindowClosed property
• right-click in the window to open a context menu
• click on the window close button in the top left corner of the window

Expected behaviour:
The context menu should be closed together with the application window (in fact, before the application window)

Actual behaviour:
Application window is closed, but the context menu remains.