JS/Ionic:TypeError: Cannot read property ‘code’ of undefined

.service('LoginService', function ($q, $http) {
return {
    loginUser: function (loginData) {
        var deferred = $q.defer(),
            promise = deferred.promise;

        $http({
            url: 'http://localhost/login.php',
            method: "POST",
            data: loginData,
            headers: {'Content-Type': 'application/json'}
        })
            .then(function (response) {
                if (response.data.error.code === "000") {
                    console.log("User login successful: " + JSON.stringify(response.data));
                    deferred.resolve(response.data);
                } else {
                    console.log("User login failed: " + JSON.stringify(response.data.error));
                    deferred.reject(response.data);
                }
            }, function (error) {
                console.log("Server error on Login " + JSON.stringify(error));
                deferred.reject(error);
            });

        promise.success = function (fn) {
            promise.then(fn);
            return promise;
        };
        promise.error = function (fn) {
            promise.then(null, fn);
            return promise;
        };
        return promise;
    }
  };
});