patch 9.0.0437: no error when custom completion function returns wrong type

Problem:    No error when a custom completion function returns something else
            than the expected list.
Solution:   Give an error. (closes #11100)
diff --git a/src/version.c b/src/version.c
index cd340b5..2d9b3ad 100644
--- a/src/version.c
+++ b/src/version.c
@@ -704,6 +704,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    437,
+/**/
     436,
 /**/
     435,