patch 8.1.0892: failure when closing a window when location list is in use

Problem:    Failure when closing a window when location list is in use.
Solution:   Handle the situation gracefully. Make sure memory for 'switchbuf'
            is not freed at the wrong time. (Yegappan Lakshmanan,
            closes #3928)
diff --git a/src/proto/window.pro b/src/proto/window.pro
index 4527a37..27f77c4 100644
--- a/src/proto/window.pro
+++ b/src/proto/window.pro
@@ -91,7 +91,7 @@
 int win_getid(typval_T *argvars);
 int win_gotoid(typval_T *argvars);
 void win_id2tabwin(typval_T *argvars, list_T *list);
-win_T *win_id2wp(typval_T *argvars);
+win_T *win_id2wp(int id);
 int win_id2win(typval_T *argvars);
 void win_findbuf(typval_T *argvars, list_T *list);
 void get_framelayout(frame_T *fr, list_T *l, int outer);