property "AdminWebUser.role" is not defined

After sometime of ideal page this error is coming

Property "CWebUser.role" is not defined.

D:\xampp\htdocs\project\framework\web\auth\CWebUser.php(146)

Here is my code below

DefaultController:

class DefaultController extends Controller

{

[indent]

public function actionLogin() {

[indent]$this->layout = ‘//layouts/limitless_login’;

if (!isset(Yii::app()->user->id)) {

$model = new AdminLoginForm;

if (isset($_POST[‘AdminLoginForm’])) {

        	[indent]$model->attributes = $_POST['AdminLoginForm'];


            if ($model->validate() && $model->login()) {


            	$this->redirect(Yii::app()->user->returnUrl);


          }[/indent]


        }


        $this->render('login', array('model' => $model,'authUrl'=>$authUrl));

}

[/indent]

[/indent]

}

AdminLoginForm:

class AdminLoginForm extends CFormModel

{

[indent]public $username;


public $password;


public $email;


public $rememberMe;





public function rules()


{


	[indent]return array(


		[indent]// username and password are required


		array('username, password', 'required'),


		// rememberMe needs to be a boolean


		array('rememberMe', 'boolean'),


		// password needs to be authenticated


		array('password', 'authenticate'),[/indent]


	);[/indent]


}





public function attributeLabels()


{


	[indent]return array(


		[indent]'rememberMe'=>'Remember me next time',


                    'username'=>'User Name',[/indent]


	);[/indent]


}





public function authenticate($attribute,$params)


{


	[indent]if(!$this->hasErrors())


	{


		[indent]$this->_identity=new UserIdentity($this->username,$this->password);


		if(!$this->_identity->authenticate())


			[indent]$this->addError('password','Incorrect username or password');[/indent][/indent]


	}[/indent]


}





public function login()


{


	[indent]if($this->_identity===null)


	{


		[indent]$this->_identity=new UserIdentity($this->username,$this->password);


		$this->_identity->authenticate();[/indent]


	}


	if($this->_identity->errorCode===UserIdentity::ERROR_NONE)


	{


		[indent]$duration=$this->rememberMe ? 3600*24*30 : 0; // 30 days


		Yii::app()->user->login($this->_identity,$duration);


		return true;[/indent]


	}


	else


		[indent]return false;[/indent][/indent]


}[/indent]

}

UserIdentity :

class UserIdentity extends CUserIdentity

{

[indent] private $_id;

private $_name;


private $_role;





public function authenticate()


{


   [indent] $user = AdminUser::model()->find('LOWER(username)=?', array(strtolower($this->username)));


if ($user === null)


    {


        [indent]$this->errorCode = self::ERROR_USERNAME_INVALID;[/indent]


    }


    else {


           [indent] $this->_id = $user->user_id;


            $this->_role = $user->role;


            $this->_name = $user->username;


            Yii::app()->user->setState('name',$user->username);


            Yii::app()->user->setState('username',$user->username);


            Yii::app()->user->setState('role',$user->role);


            $this->errorCode = self::ERROR_NONE;[/indent]


    }


    return!$this->errorCode;[/indent]


    


}





public function getId()


{


   [indent] return $this->_id;[/indent]


}





public function getUsername()  {


   [indent] return $this->_name;[/indent]


}





public function getRole()  {


    [indent]return $this->_role;[/indent]


}[/indent]

}

Can some one say why is this happening, if session time out it goes to login page. The session is on I can get user->id but not user->role, but it coming all the time after I logged in and continuous use of app, after ideal time this message is coming.

Thanks in advance