patch 9.1.0913: no error check for neg values for 'messagesopt'

Problem:  no error check for neg values for 'messagesopt'
          (after v9.1.0908)
Solution: add additional error checks and tests (h-east)

closes: #16187

Signed-off-by: Shougo Matsushita <Shougo.Matsu@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>
diff --git a/src/version.c b/src/version.c
index 6dc9a47..1333d9d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -705,6 +705,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    913,
+/**/
     912,
 /**/
     911,