patch 8.2.0012: some undo functionality is not tested

Problem:    Some undo functionality is not tested.
Solution:   Add a few more test cases. (Dominique Pelle, closes #5364)
diff --git a/src/version.c b/src/version.c
index c4c583a..27a42e0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    12,
+/**/
     11,
 /**/
     10,