EmptyBlockForm.php

<?php

namespace Drupal\block_test\PluginForm;

use Drupal\Core\Form\FormStateInterface;
use Drupal\Core\Plugin\PluginFormBase;

/**
 * Provides a form for a block that is empty.
 */
class EmptyBlockForm extends PluginFormBase {
    
    /**
     * {@inheritdoc}
     */
    public $plugin;
    
    /**
     * {@inheritdoc}
     */
    public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
        return $form;
    }
    
    /**
     * {@inheritdoc}
     */
    public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
        // Intentionally empty.
    }

}