patch 8.2.1948: GUI: crash when handling message while closing a window

Problem:    GUI: crash when handling message while closing a window. (Srinath
            Avadhanula)
Solution:   Don't handle message while closing a window. (closes #7250)
diff --git a/src/globals.h b/src/globals.h
index 379a532..dd7fa4a 100644
--- a/src/globals.h
+++ b/src/globals.h
@@ -581,6 +581,12 @@
 // ('lines' and 'rows') must not be changed.
 EXTERN int	updating_screen INIT(= FALSE);
 
+#ifdef MESSAGE_QUEUE
+// While closing windows or buffers messages should not be handled to avoid
+// using invalid windows or buffers.
+EXTERN int	dont_parse_messages INIT(= FALSE);
+#endif
+
 #ifdef FEAT_MENU
 // The root of the menu hierarchy.
 EXTERN vimmenu_T	*root_menu INIT(= NULL);