() Неустранимая ошибка: вызов функции-члена getAttribute () в null

Получение этой ошибки независимо от того, что я делаю, и снова и снова показывает одну и ту же ошибку. () Неустранимая ошибка: вызов функции-члена getAttribute () для null.
это мой studentcontroller.php.
Получение этой ошибки независимо от того, что я делаю, и снова и снова показывает одну и ту же ошибку. () Неустранимая ошибка: вызов функции-члена getAttribute () для null.
это мой studentcontroller.php.

class StudentController extends Controller
{
/**
* @var string the default layout for the views. Defaults to '//layouts/column2', meaning
* using two-column layout. See 'protected/views/layouts/column2.php'.
*/
public $layout='//layouts/column2';

/**
* @return array action filters
*/
public function filters()
{
return array(
'accessControl', // perform access control for CRUD operations
'postOnly + delete', // we only allow deletion via POST request
);
}

/**
* Specifies the access control rules.
* This method is used by the 'accessControl' filter.
* @return array access control rules
*/
public function accessRules()
{
return array(
array('allow', // allow authenticated user to perform 'create' and 'update' actions
'actions'=>array('create','update','viewjobs','viewoffers','index','view'),
'users'=>array('@'),
),
array('allow', // allow admin user to perform 'admin' and 'delete' actions
'actions'=>array('admin','delete'),
'users'=>array('admin'),
),
array('deny',  // deny all users
'users'=>array('*'),
),
);
}

/**
* Displays a particular model.
* @param integer $id the ID of the model to be displayed
*/
public function actionView($id)
{
$this->render('view',array(
'model'=>$this->loadModel($id),
));
}

/**
* Creates a new model.
* If creation is successful, the browser will be redirected to the 'view' page.
*/
public function actionCreate()
{
$model=new Student;

// Uncomment the following line if AJAX validation is needed
// $this->performAjaxValidation($model);

if(isset($_POST['Student']))
{
$model->attributes=$_POST['Student'];
if($model->save())
$this->redirect(array('view','id'=>$model->st_id));
}

$this->render('create',array(
'model'=>$model,
));
}

/**
* Updates a particular model.
* If update is successful, the browser will be redirected to the 'view' page.
* @param integer $id the ID of the model to be updated
*/
public function actionUpdate($id)
{
$model=$this->loadModel($id);

// Uncomment the following line if AJAX validation is needed
// $this->performAjaxValidation($model);

if(isset($_POST['Student']))
{
$model->attributes=$_POST['Student'];
if($model->save())
$this->redirect(array('view','id'=>$model->st_id));
}

$this->render('update',array(
'model'=>$model,
));
}

/**
* Deletes a particular model.
* If deletion is successful, the browser will be redirected to the 'admin' page.
* @param integer $id the ID of the model to be deleted
*/
public function actionDelete($id)
{
$this->loadModel($id)->delete();
$model=Login::model()->find("id=?",array($id));
$model->delete();
// if AJAX request (triggered by deletion via admin grid view), we should not redirect the browser
if(!isset($_GET['ajax']))
$this->redirect(isset($_POST['returnUrl']) ? $_POST['returnUrl'] : array('admin'));
}

/**
* Lists all models.
*/

// OLD ACTION INDEX
/*public function actionIndex()
{
$dataProvider=new CActiveDataProvider('Student');
$this->render('index',array(
'dataProvider'=>$dataProvider,
));
}*/

public function actionIndex()
{
$dataProvider=new CActiveDataProvider('Student',array(
'criteria'=>array(
'condition'=>'st_id='.Yii::app()->user->id,

)));
$this->render('index',array(
'dataProvider'=>$dataProvider,
));
}

/**
* Manages all models.
*/
public function actionAdmin()
{
$model=new Student('search');
$model->unsetAttributes();  // clear any default values
if(isset($_GET['Student']))
$model->attributes=$_GET['Student'];

$this->render('admin',array(
'model'=>$model,
));
}

public function actionViewjobs(){
//PPO accept Check
$ppoCheck=  Yii::app()->db->createCommand("select * from offers where st_id = ".Yii::app()->user->id." and ppo = 'Y' and accepted = 'Y'")->queryAll();
if(count($ppoCheck)!=0)
{

Yii::app()->user->setFlash('notice','You have already accepted your PPO and hence, will be able to apply to ONLY ONE company');
}

$stud = Student::model()->findByPk(Yii::app()->user->id);
$st = new Student();
$st->st_id = Yii::app()->user->id;

$dept = $stud->getAttribute("dept");
$programme = $stud->getAttribute("programme");

$sql =  Yii::app()->db->createCommand("select count(*) as cnt from student where dept=\"".$dept."\" and programme = \"".$programme."\"")->queryRow();
$totalReg = $sql['cnt'];

$sql =  Yii::app()->db->createCommand("select count(*) as cnt from (select distinct(oTemp.st_id) from offers as oTemp) as o, student as s where o.st_id = s.st_id and s.dept=\"".$dept."\" and s.programme = \"".$programme."\"")->queryRow();
$actualStudPlaced = $sql['cnt'];

if($totalReg==0) $percent=0;
else $percent = ($actualStudPlaced*100)/$totalReg;

if($percent>=80)
{
Yii::app()->user->setFlash('notice','Your dept is on a roll. More than 80% placed! You may now apply for a new job profile even if you accepted an offer before.');
}$sqlcount =  Yii::app()->db->createCommand("select count(*) from job_profile_branches where dept = \"".$dept."\"")->queryScalar();
$sql = "select * from job_profile as j, company as c where j.approved='Y' and (c.c_id,j.j_id) in (select c_id, j_id from job_profile_branches where dept = \"".$dept."\")";

$dataProvider = new CSqlDataProvider($sql, array(
'db' => Yii::app()->db,
'keyField' => 'c_id',
'totalItemCount' => $sqlcount
));

$this->render('viewJobProfiles',array(
'dataProvider'=>$dataProvider,
));
}

public function actionViewoffers(){

$id = Yii::app()->user->id;

$sqlcount =  Yii::app()->db->createCommand("select count(*) from job_profile as j, offers as o where j.j_id=o.j_id and j.c_id=o.c_id and o.st_id=".$id)->queryScalar();
$sql = "select * from job_profile as j, offers as o,company as c where j.j_id=o.j_id and j.c_id=o.c_id and c.c_id=j.c_id and o.st_id=".$id;
$dataProvider = new CSqlDataProvider($sql, array(
'db' => Yii::app()->db,
'keyField' => 'j_id',
'totalItemCount' => $sqlcount
));

$this->render('viewOffers',array(
'dataProvider'=>$dataProvider,
));
}
/**
* Returns the data model based on the primary key given in the GET variable.
* If the data model is not found, an HTTP exception will be raised.
* @param integer $id the ID of the model to be loaded
* @return Student the loaded model
* @throws CHttpException
*/
public function loadModel($id)
{
$model=Student::model()->findByPk($id);
if($model===null)
throw new CHttpException(404,'The requested page does not exist.');
return $model;
}

/**
* Performs the AJAX validation.
* @param Student $model the model to be validated
*/
protected function performAjaxValidation($model)
{
if(isset($_POST['ajax']) && $_POST['ajax']==='student-form')
{
echo CActiveForm::validate($model);
Yii::app()->end();
}
}
}