angularjs - Issue with angular animation and undefined javascript values -

i trying angular animation triggered upon unsuccessful login (either when server sends 4xx (e.g. 403) or when no credentials provided).

here controller:

 .controller('signinctrl', ['$scope', '$rootscope', '$cookies', '$state', '$animate', 'signinservice', function ($scope, $rootscope, $cookies, $state, $animate, signinservice) {         $scope.signin = function () {             $scope.shake = false;             if ($scope.credentials) {                 signinservice.signin($scope.credentials, function (status, memberrole) {                         $scope.shake = false;                         //todo: necessary check status?                         if (status === 200) {                            ...                         }                     },                     function () {                         $scope.shake = true;                     });             }             else {                 //todo: shakes/works once!                 $scope.shake = true;             }         }     }]); 

the form:

<form class="form-signin" ng-class="{shake: shake}" name="signinform" ng-submit="signin()" novalidate>     <h2 class="form-signin-heading signin-title">{{'signin' | translate}}</h2>     <input type="email" ng-required name="username" ng-model="credentials.username" class="form-control" placeholder="{{'signin_form_email'| translate}}"/>     <input type="password" ng-required name="password" ng-model="credentials.password" class="form-control" placeholder="{{'signin_form_password'| translate}}"/>     <button class="btn btn-lg btn-primary btn-block" type="submit">{{'signin' | translate}}</button>     <div class="forgot-password">         <a ui-sref="sendpasswordresetinformation">{{'signin_form_forgotten_password' | translate}}</a>     </div> </form> 

however, if form has no credentials in inputs (nothing in not empty string) form shakes once.

can please help?

edit 1:

  .factory('signinservice', ['$http', function ($http) {         return {             signin: function (credentials, successcallback, errorcallback) {                  var transform = function (data) {                     return $.param(data);                 }                  return $http.post('/api/signin', credentials, {                     headers: {'content-type': 'application/x-www-form-urlencoded; charset=utf-8'},                     transformrequest: transform                 }).success(function (data, status, headers) {                     if (status === 200) {                         successcallback(status, headers('member_role'));                     }                     else {                         console.log('auth error');                         successcallback('error');                     }                 }).error(function(data, status, headers) {                     console.log("error!", data, status, headers);                     errorcallback();                 });             }         }     }]); 

changing controller :

... $scope.signin = function () {             $scope.shake = false;             $scope.$apply();//added!             ... 

fixed issue. floribon...