Steps to reproduce:
Load the attached file with qmlscene, click on any menu and move the mouse around to the other menus. The bug is not triggered imediattely, so you must keep moving untill it breaks ( can take up to 1 to 50 trials, I'v managed to crash qmlscene in every attempt in less than 15 secs. )
Whem using the qmlscene from Qt 5.1 and the attached file, an warning is issued: "QQuickWindow::sendEvent: Cannot send event to a null item"
But with the same file, if used from a qmlscene from Qt 5.2 an assert is thrown, ASSERT: "oldActiveFocusItem" in file items/qquickwindow.cpp, line 773
The file attached is simly a ApplicationWindow with a MenuBar populated with Actions - nothing fancy, and really small code.