Explorer Bugs: Moving with mouse through Start Menu causes kernel mode crash

Cause of this bug?
set_focus_window (line ~780) - subsys/win32k/ntuser/window.c
It crashes on line
Window->MessageQueue->FocusWindow = New;
and now you can guess what window doesn't have message queue? Yes, it's the
desktop one! And how do we got there? It's called from WinPosShowWindow
function (when submenu of the Start Menu is hidden). It should be fairly
easy to fix, but I will not do that because there is plan to move desktop
handling into CSRSS and that will fix this bug in more clever way.