PATCH: win32k: crash when destroying W32 process

Happens on 2nd stage when you open/close keyboard setting dialogs.

PspExitThread // ps/kill.c:693
Win32kThreadCallback // dllmain.c:442

PsSetThreadWin32Thread(Thread, NULL);

[...]

PspExitThread // ps/kill.c:700
Win32kProcessCallback // dllmain.c:174
IntCleanupCurIcons // cursoricon.c:331
IntDestroyCurIconObject // cursoricon.c:288
UserSetCursor // msgqueue.c:113

pti = PsGetCurrentThreadWin32Thread();
MessageQueue = pti->MessageQueue; // crash!