patch 8.1.2420: crash when calling popup_close() in win_execute()

Problem:    Crash when calling popup_close() in win_execute().
Solution:   Disallow popup_close() in popup window. (Yasuhiro Matsumoto,
            closes #5345)
diff --git a/src/version.c b/src/version.c
index 2b992df..7b36fe3 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2420,
+/**/
     2419,
 /**/
     2418,