patch 9.0.0018: going over the end of the typahead

Problem:    Going over the end of the typahead.
Solution:   Put a NUL after the typeahead.
diff --git a/src/version.c b/src/version.c
index 5d10909..6415b59 100644
--- a/src/version.c
+++ b/src/version.c
@@ -736,6 +736,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    18,
+/**/
     17,
 /**/
     16,