comctl32: Don't pass unrelated control to UnChanged.

dlls/comctl32/propsheet.c

@@ -3492,7 +3492,7 @@ PROPSHEET_DialogProc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
        * from which to switch to the next page */
       SendMessageW(hwndTabCtrl, TCM_SETCURSEL, psInfo->active_page, 0);
 
-      PROPSHEET_UnChanged(hwnd, (HWND)wParam);
+      PROPSHEET_UnChanged(hwnd, NULL);
 
       return TRUE;
     }