came across small potential kmode crash while researching another bug fix

reactos/subsys/win32k/eng

diff -u -r1.61 -r1.62
--- bitblt.c	12 Dec 2004 23:08:09 -0000	1.61
+++ bitblt.c	14 Dec 2004 03:23:14 -0000	1.62
@@ -16,7 +16,7 @@

  *  along with this program; if not, write to the Free Software
  *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  */

-/* $Id: bitblt.c,v 1.61 2004/12/12 23:08:09 navaraf Exp $

+/* $Id: bitblt.c,v 1.62 2004/12/14 03:23:14 royce Exp $

  *
  * COPYRIGHT:        See COPYING in the top level directory
  * PROJECT:          ReactOS kernel

@@ -514,7 +514,7 @@

   UsesSource = ((Rop4 & 0xCC0000) >> 2) != (Rop4 & 0x330000);
   if (UsesSource)
     {

-      if (NULL == SourcePoint || NULL == SourceObj)

+      if (NULL == SourcePoint || NULL == SourceSurf)

         {
           return FALSE;
         }