patch 8.1.1709: Coverity warns for possibly using a NULL pointer

Problem:    Coverity warns for possibly using a NULL pointer.
Solution:   Make sure no NULL pointer is used.
diff --git a/src/version.c b/src/version.c
index d1f5eba..0ac981e 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1709,
+/**/
     1708,
 /**/
     1707,