patch 8.2.3994: Vim9: extend() complains about type when it was not declared

Problem:    Vim9: extend() complains about the type even when it was not
            declared.
Solution:   Only check the list or dict type when it was declared.
diff --git a/src/version.c b/src/version.c
index b7bc986..04f06f9 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    3994,
+/**/
     3993,
 /**/
     3992,