patch 8.2.3720: Vim9: Internal error when invoking closure in legacy context

Problem:    Vim9: Internal error when invoking closure in legacy context.
Solution:   Give a more appropriate error message. (closes #9251)
diff --git a/src/version.c b/src/version.c
index d977c65..810567f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -754,6 +754,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3720,
+/**/
     3719,
 /**/
     3718,