patch 8.1.1889: Coverity warns for using a NULL pointer

Problem:    Coverity warns for using a NULL pointer.
Solution:   Use zero for column if pos is NULL.
diff --git a/src/version.c b/src/version.c
index 85d481a..d7bdfa2 100644
--- a/src/version.c
+++ b/src/version.c
@@ -766,6 +766,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1889,
+/**/
     1888,
 /**/
     1887,