Issue #3403999 by acbramley, Primsi, LeDucDuBleuet, godotislate, Lendude:...

   * {@inheritdoc}

   */

  public function buildForm(array $form, FormStateInterface $form_state) {

    // Don't show the form when batch operations are in progress.

    if (($batch = batch_get()) && isset($batch['current_set'])) {

      return [

        // Set the theme callback to be nothing to avoid errors in template_preprocess_views_exposed_form().

        '#theme' => '',

      ];

    }

    // Make sure that we validate because this form might be submitted

    // multiple times per page.

    $form_state->setValidationEnforced();