[WIN32SS] Fix crash if releasing a PDEVOBJ before switching to graphic mode

- do not try to remove ppdev from gppdevList if gppdevList is NULL
- do not check (and maybe change) gpmdev, as it should be done only in MDEVOBJ_vDestroy

win32ss/gdi/eng/pdevobj.c

@@ -139,7 +139,7 @@ PDEVOBJ_vRelease(
         {
             gppdevList = ppdev->ppdevNext;
         }
-        else
+        else if (gppdevList)
         {
             PPDEVOBJ ppdevCurrent = gppdevList;
             BOOL found = FALSE;
@@ -154,10 +154,6 @@ PDEVOBJ_vRelease(
                 ppdevCurrent->ppdevNext = ppdev->ppdevNext;
         }
 
-        /* Is this the primary one ? */
-        if (ppdev == gpmdev->ppdevGlobal)
-            gpmdev->ppdevGlobal = NULL;
-
         /* Unload display driver */
         EngUnloadImage(ppdev->pldev);