patch 8.2.2018: Vim9: script variable not found from lambda

Problem:    Vim9: script variable not found from lambda.
Solution:   In a lambda also check the script hashtab for a variable without a
            scope. (closes #7329)

src/testdir/test_vim9_func.vim

@@ -1476,6 +1476,15 @@ def Test_line_continuation_in_def()
   Line_continuation_in_def('.')->assert_equal('full')
 enddef
 
+def Test_script_var_in_lambda()
+  var lines =<< trim END
+      vim9script
+      var script = 'test'
+      assert_equal(['test'], map(['one'], {-> script}))
+  END
+  CheckScriptSuccess(lines)
+enddef
+
 def Line_continuation_in_lambda(): list<string>
   var x = range(97, 100)
       ->map({_, v -> nr2char(v)