Qt 4.7.0 / MacOS/X: previously dismissed popup menus come back as zombies after their parent windows have been hidden and re-shown.

Note: This bug affects MacOS/X under Qt-4.7.0-beta1/Cocoa. I also tested under Qt-4.6.2/cocoa and the bug does not occur there, so I think this is a new regression for 4.7.x.

To reproduce the bug:

1) Download and compile the attached example program (popup_bug.zip) using Qt 4.7.0-beta1
2) Run the program: A window appears (in Windows XP style) with two buttons
3) Click the "Show Dialog" button. A second window appears containing a single button.
4) Click the "Show Popup Menu" button in the second window. A popup-menu appears with four options
5) Pick an option in the popup-menu (it doesn't matter which one). The menu dissappears.
6) Now go back to original (two-button) window and click "Hide Dialog", and then "Show Dialog".
7) The second window disappears and then re-appears, as expected, but the popup-menu also reappears – that is incorrect behavior. What's worse is that the popup-menu no longer responds to user input... clicking on it does not select a menu item or cause the menu to go away.

The expected behavior after step (6) is complete is that the second window should appear, but the popup-menu should not (at least, not until "Show Popup Menu" is clicked again!)