Simply display zero if it's less or equals to 0.
// (or their absence).
                hint = true;
                if 
                {
                    if (test_hint.serverError())
                    {
                        if (!server_exception)
                        {
                            es_hint = false;
                            fmt::print(stderr, "Expected server error code '{}' but got no server error (query: {}).\n",
                                       test_hint.serverError(), full_query
                        }
                        else if (server_exception->code() != test_hint.serverError())
                        {
                            es_hint = false;
                            fmt::print(stderr, "Expected server error code: {} but got: {} (query: {}).\n",
                                       test_hint.serverError(), server_exception->code(), full_query
                        }
                    }
                    if (test_hint.clientError())
                    {
                        if (!client_exception)
                        {
                            es_hint = false;
                            fmt::print(stderr, "Expected client error code '{}' but got no client error (query: {}).\n",
                                       test_hint.clientError(), full_query
                        }
                        else if (client_exception->code() != test_hint.clientError())
                        {
                            es_hint = false;