patch 9.1.0539: Not enough tests for what v9.1.0535 fixed

Problem:  Not enough tests for what v9.1.0535 fixed
Solution: Add another test for ex-mode

This comes from: https://groups.google.com/g/vim_dev/c/F5-tDqoafz8/m/GqKF-uQsLD0J

related: #15120

Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 7d1c91b..456f2d6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    539,
+/**/
     538,
 /**/
     537,