patch 8.2.2504: Vim9: crash when using an argument from a closure

Problem:    Vim9: crash when using an argument from a closure.
Solution:   Check if gen_load_outer is NULL. (closes #7821)
diff --git a/src/version.c b/src/version.c
index 60f8a71..465b5b0 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2504,
+/**/
     2503,
 /**/
     2502,