patch 8.2.4526: Vim9: cannot set variables to a null value

Problem:    Vim9: cannot set variables to a null value.
Solution:   Add null_list, null_job, etc.
diff --git a/src/testdir/test_vim9_func.vim b/src/testdir/test_vim9_func.vim
index 866cf4c..a47dbae 100644
--- a/src/testdir/test_vim9_func.vim
+++ b/src/testdir/test_vim9_func.vim
@@ -3326,7 +3326,7 @@
       var Expr: func(dict<any>): dict<any>
       const Call = Foo(Expr)
   END
-  v9.CheckScriptFailure(lines, 'E1235:')
+  v9.CheckScriptFailure(lines, 'E1031:')
 enddef
 
 def Test_partial_double_nested()