Set the default menu item of the window menu

diff --git a/windows/mdi.c b/windows/mdi.c
index 000b368..a4fecba 100644
--- a/windows/mdi.c
+++ b/windows/mdi.c
@@ -849,6 +849,7 @@
     EnableMenuItem(hSysPopup, SC_SIZE, MF_BYCOMMAND | MF_GRAYED);
     EnableMenuItem(hSysPopup, SC_MOVE, MF_BYCOMMAND | MF_GRAYED);
     EnableMenuItem(hSysPopup, SC_MAXIMIZE, MF_BYCOMMAND | MF_GRAYED);
+    SetMenuDefaultItem(hSysPopup, SC_CLOSE, FALSE);
 
     /* redraw menu */
     DrawMenuBar(frame->hwndSelf);