patch 8.2.2299: Vim9: invalid memory access making error message flaky

Problem:    Vim9: invalid memory access making error message flaky.
Solution:   Do not check cmd_argt for CMD_USER. (issue #7467)

src/testdir/test_vim9_cmd.vim

@@ -771,6 +771,24 @@ def Test_f_args()
   CheckScriptSuccess(lines)
 enddef
 
+def Test_user_command_comment()
+  command -nargs=1 Comd echom <q-args>
+
+  var lines =<< trim END
+    vim9script
+    Comd # comment
+  END
+  CheckScriptSuccess(lines)
+
+  lines =<< trim END
+    vim9script
+    Comd# comment
+  END
+  CheckScriptFailure(lines, 'E1144:')
+
+  delcommand Comd
+enddef
+
 def Test_star_command()
   var lines =<< trim END
     vim9script
@@ -798,12 +816,14 @@ def Test_cmd_argument_without_colon()
 enddef
 
 def Test_ambiguous_user_cmd()
+  command Cmd1 eval 0
+  command Cmd2 eval 0
   var lines =<< trim END
-      com Cmd1 eval 0
-      com Cmd2 eval 0
       Cmd
   END
-  CheckScriptFailure(lines, 'E464:')
+  CheckDefAndScriptFailure(lines, 'E464:', 1)
+  delcommand Cmd1
+  delcommand Cmd2
 enddef
 
 def Test_command_not_recognized()