patch 8.2.4534: Vim9: "is" operator with empty string and null returns true

Problem:    Vim9: "is" operator with empty string and null returns true.
Solution:   Consider empty string and null to be different for "is".
diff --git a/src/version.c b/src/version.c
index 9b72517..5e5a2a8 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    4534,
+/**/
     4533,
 /**/
     4532,