Issue #3275650: Group Message view crashes when empty.

          admin_label: Message

          entity_type: mailgroup

          plugin_id: standard

          required: false

          required: true

      display_description: ''

      display_extenders: {  }

      path: mailgroup/%/messages

<?php

/**

 * @file

 * Install, update, and uninstall hooks for the Mail Group module.

 */

/**

 * Make Message relationship required for Message View.

 */

function mailgroup_update_9001() {

  if (\Drupal::moduleHandler()->moduleExists('views')) {

    $entity_type_manager = \Drupal::entityTypeManager();

    $view_storage = $entity_type_manager->getStorage('view');

    $view = $view_storage

      ->load('mailgroup')

      ->getExecutable();

    $view->setHandlerOption('messages', 'relationship', 'message', 'required', TRUE);

    $view->save();

  }

}