patch 9.0.0020: with some completion reading past end of string

Problem:    With some completion reading past end of string.
Solution:   Check the length of the string.
diff --git a/src/version.c b/src/version.c
index 42e9135..26cb768 100644
--- a/src/version.c
+++ b/src/version.c
@@ -736,6 +736,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    20,
+/**/
     19,
 /**/
     18,