Assertion 'pDesk != NULL' failed at C:/Users/ziliang/workspace/reactos/0.3.17/reactos/win32ss/user/ntuser/object.c line 110

Entered debugger on embedded INT3 at 0x0008:0x809597e2.
kdb:> bt
Eip:
<NTOSKRNL.EXE:1597e3 (:0 (DbgUserBreakPoint))>
Frames:
<win32k.sys:7ca56 (:0 (AllocDeskProcObject))>
<win32k.sys:7da06 (:0 (UserCreateObject))>
<win32k.sys:310f8 (win32ss/user/ntuser/callproc.c:38 (CreateCallProc))>
<win32k.sys:311fd (win32ss/user/ntuser/callproc.c:134 (UserGetCPD))>
<win32k.sys:325cd (win32ss/user/ntuser/class.c:442 (IntGetClassWndProc))>
<win32k.sys:3521d (win32ss/user/ntuser/class.c:2010 (NtUserGetClassInfo))>
<NTOSKRNL.EXE:142065 (ntoskrnl/include/internal/arch/../i386/ke.h:689 (KiSystemServiceHandler))>
<NTOSKRNL.EXE:3d95 (:0 (KiFastCallEntry))>
<ntdll.dll:c7d1>
<user32.dll:60837>
<user32.dll:626ba>
<ob1.exe:82286>
<ob1.exe:7f974>
<ob1.exe:7fc3e>
<ob1.exe:83729>
<00000202>
Couldn't access memory at 0x0003019E!
kdb:> cont

Entered debugger on last-chance exception (Exception Code: 0xc0000005) (Page Fault)
Memory at 0x00000040 could not be read: Page not present.
kdb:> bt
Eip:
<win32k.sys:7ca98 (:0 (AllocDeskProcObject))>
Frames:
<win32k.sys:7da06 (:0 (UserCreateObject))>
<win32k.sys:310f8 (win32ss/user/ntuser/callproc.c:38 (CreateCallProc))>
<win32k.sys:311fd (win32ss/user/ntuser/callproc.c:134 (UserGetCPD))>
<win32k.sys:325cd (win32ss/user/ntuser/class.c:442 (IntGetClassWndProc))>
<win32k.sys:3521d (win32ss/user/ntuser/class.c:2010 (NtUserGetClassInfo))>
<NTOSKRNL.EXE:142065 (ntoskrnl/include/internal/arch/../i386/ke.h:689 (KiSystemServiceHandler))>
<NTOSKRNL.EXE:3d95 (:0 (KiFastCallEntry))>
<ntdll.dll:c7d1>
<user32.dll:60837>
<user32.dll:626ba>
<ob1.exe:82286>
<ob1.exe:7f974>
<ob1.exe:7fc3e>
<ob1.exe:83729>
<00000202>
Couldn't access memory at 0x0003019E!
kdb:>