Added missing WIN_ReleaseWndPtr.

diff --git a/windows/mdi.c b/windows/mdi.c
index 291007e..cf52d53 100644
--- a/windows/mdi.c
+++ b/windows/mdi.c
@@ -1129,9 +1129,10 @@
       case WM_SETFOCUS:
 	if( ci->hwndActiveChild )
 	{
-	   w = WIN_FindWndPtr( ci->hwndActiveChild );
-	   if( !(w->dwStyle & WS_MINIMIZE) )
+	   WND*	pw = WIN_FindWndPtr( ci->hwndActiveChild );
+	   if( !(pw->dwStyle & WS_MINIMIZE) )
 	       SetFocus( ci->hwndActiveChild );
+	   WIN_ReleaseWndPtr(pw);
 	} 
         retvalue = 0;
         goto END;