patch 8.1.1598: update to test file missing

Problem:    Update to test file missing.
Solution:   Update the popup window test file.
diff --git a/src/version.c b/src/version.c
index b4d568c..f74cb66 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1598,
+/**/
     1597,
 /**/
     1596,