/**
  * @see sfValidatorBase
  */
 protected function isEmpty($value)
 {
     // empty if the value is not an array
     // or if the value comes from PHP with an error of UPLOAD_ERR_NO_FILE
     if ($value instanceof sfFilebasePluginUploadedFile) {
         return $value->isError(sfFilebasePluginUploadedFile::UPLOAD_ERR_NO_FILE);
     } else {
         return sfFilebasePluginUploadedFilesManager::isUploadedFile($value);
     }
 }