patch 9.0.0504: still a build failure

Problem:    still a Build failure.
Solution:   Add another missing changes.  Avoid compiler warning.
diff --git a/src/version.c b/src/version.c
index 6bd68dc..a8e0151 100644
--- a/src/version.c
+++ b/src/version.c
@@ -700,6 +700,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    504,
+/**/
     503,
 /**/
     502,