updated for version 7.4.369

Problem:    Using freed memory when exiting while compiled with EXITFREE.
Solution:   Set curwin to NULL and check for that. (Dominique Pelle)

src/window.c

@@ -2489,6 +2489,10 @@ win_free_all()
 
     while (firstwin != NULL)
 	(void)win_free_mem(firstwin, &dummy, NULL);
+
+    /* No window should be used after this. Set curwin to NULL to crash
+     * instead of using freed memory. */
+    curwin = NULL;
 }
 #endif