/**
  * {@inheritdoc}
  */
 public function acceptExposedInput($input)
 {
     if (empty($this->options['exposed'])) {
         return TRUE;
     }
     // If view is an attachment and is inheriting exposed filters, then assume
     // exposed input has already been validated.
     if (!empty($this->view->is_attachment) && $this->view->display_handler->usesExposed()) {
         $this->validatedExposedInput = (array) $this->view->exposed_raw_input[$this->options['expose']['identifier']];
     }
     // If it's non-required and there's no value don't bother filtering.
     if (!$this->options['expose']['required'] && empty($this->validatedExposedInput)) {
         return FALSE;
     }
     return parent::acceptExposedInput($input);
 }