FormTestEmptySelectForm.php

<?php

namespace Drupal\form_test\Form;

use Drupal\Core\Form\FormBase;
use Drupal\Core\Form\FormStateInterface;

/**
 * Builds a form to test select elements when #options is not an array.
 *
 * @internal
 */
class FormTestEmptySelectForm extends FormBase {
  
  /**
   * {@inheritdoc}
   */
  public function getFormId() {
    return 'form_test_empty_select';
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildForm(array $form, FormStateInterface $form_state) {
    $form['empty_select'] = [
      '#type' => 'select',
      '#title' => t('Empty Select'),
      '#multiple' => FALSE,
      '#options' => NULL,
    ];
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitForm(array &$form, FormStateInterface $form_state) {
  }

}