title: Yii file CFormInputElement won't display unless explicitly marked "safe"
body: <p>I'm trying to use Form Builder to build a simple file upload prompt. I want to specify the rule for the file to be similar to</p>
  
  <pre><code>array('formFile', 'file', 'allowEmpty' =&gt; false, 'types' =&gt; 'html'),
  </code></pre>
  
  <p>but something is wrong. The file upload element only appears if I explicitly mark the element as <code>'safe'</code> (and remove the <code>'file'</code> rule). What am I missing?</p>
  
  <p><em>models/UploadForm.php</em></p>
  
  <pre><code>class UploadForm extends CFormModel
  {
      public $year;
      public $formFile;
  
      public function rules ()
      {
          return array(
              array('year',    'required'),
              array('year',    'date', 'format'=&gt;'yyyy'),
  //            array('formFile', 'safe'),
              array('formFile', 'file', 'allowEmpty' =&gt; false, 'types' =&gt; 'html'),
          );
      }
  
      static public function getYearOptions () {...}
  }
  </code></pre>
  
  <p><em>views/extranet/uploadForm.php</em></p>
  
  <pre><code>return array(
      'title' =&gt; 'Select year',
      'method' =&gt; 'post',
      'enctype' =&gt; 'multipart/form-data',
  
      'elements' =&gt; array(
          'year' =&gt; array(
              'type'  =&gt; 'dropdownlist',
              'items' =&gt; UploadForm::getYearOptions(),
          ),
          'formFile' =&gt; array(
              'type'  =&gt; 'file',
              'label' =&gt; 'form source file',
          ),
      ),
  
      'buttons' =&gt; array(
          'upload' =&gt; array(
              'type'  =&gt; 'submit',
              'label' =&gt; 'upload',
          ),
      ),
  );
  </code></pre>
  
  <p><em>controllers/ExtranetController.php</em></p>
  
  <pre><code>class ExtranetController extends CController
  {
      public function actionIndex ()
      {
          $form = new CForm('application.views.extranet.uploadForm', new UploadForm());
          if ($form-&gt;submitted('upload') &amp;&amp; $form-&gt;validate()) {...}
          $this-&gt;render('index', array('form' =&gt; $form));
      }
  }
  </code></pre>