title: Yii::app()->user->isGuest is returning null
body: <p><strong>Yii::app()->user->isGuest</strong> is throwing exception as</p>
  
  <p><code>"Uncaught exception 'CException' with message 'Property "CWebUser.email" is not defined."</code></p>
  
  <p>how can i solve this error?</p>