On Qt for Cocoa, the application crashes when a menu is present twice in the menu bar

On Mac OS X, with Cocoa, when a menu is added in diffferent place of the interfaces, the application crashes.

On Cocoa, [NSMenuItem setSubenu] raises an exception if the menu already have a sub menu( http://developer.apple.com/documentation/Cocoa/Reference/ApplicationKit/Classes/NSMenuItem_Class/Reference/Reference.html#//apple_ref/occ/instm/NSMenuItem/setSubmenu: )

Here is an example to reproduce the issue:

#include <QtGui>

int main(int argc, char **argv) {
QApplication app(argc, argv);
QMainWindow main;

QMenu menu("menu");
menu.addAction("entry");
main.menuBar()->addMenu(&menu);

QMenu mainMenu("mainmenu");
main.menuBar()->addMenu(&mainMenu);
mainMenu.addMenu(&menu);
main.show();
return app.exec();
}