patch 9.0.1511: crash when using wrong arg types to assert_match()

Problem:    Crash when using wrong arg types to assert_match().
Solution:   Check for NULL pointer. (closes #12349)
diff --git a/src/version.c b/src/version.c
index 5253c49..9f4a449 100644
--- a/src/version.c
+++ b/src/version.c
@@ -696,6 +696,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1511,
+/**/
     1510,
 /**/
     1509,