patch 9.0.0554: using freed memory when command follows lambda

Problem:    Using freed memory when command follows lambda.
Solution:   Don't free what is still in use. (closes #11201)

src/testdir/test_vim9_func.vim

@@ -1515,6 +1515,20 @@ def Test_lambda_invalid_block()
   v9.CheckDefAndScriptFailure(lines, 'E488: Trailing characters: | echo')
 enddef
 
+def Test_lambda_with_following_cmd()
+  var lines =<< trim END
+      set ts=2
+      var Lambda = () => {
+          set ts=4
+        } | set ts=3
+      assert_equal(3, &ts)
+      Lambda()
+      assert_equal(4, &ts)
+  END
+  v9.CheckDefAndScriptSuccess(lines)
+  set ts=8
+enddef
+
 def Test_pass_legacy_lambda_to_def_func()
   var lines =<< trim END
       vim9script