patch 8.1.2197: ExitPre autocommand may cause accessing freed memory

Problem:    ExitPre autocommand may cause accessing freed memory.
Solution:   Check the window pointer is still valid. (closes #5093)
diff --git a/src/version.c b/src/version.c
index f2a8d6c..549b7ee 100644
--- a/src/version.c
+++ b/src/version.c
@@ -742,6 +742,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2197,
+/**/
     2196,
 /**/
     2195,