Uncaught ReferenceError: Sortable is not defined

Problem/Motivation

This error message appears when using the ckeditor plugin.

Proposed resolution

In the file /media_folders/js/ckeditor.js instead of this:

(function ($, Drupal, Sortable) {
  Drupal.behaviors.media_folders_editor = {
    attach(context, settings) {

    ...

  };
})(jQuery, Drupal, Sortable);

I suggest this:

(function ($, Drupal) {
  Drupal.behaviors.media_folders_editor = {
    attach(context, settings) {

    ...

  };
})(jQuery, Drupal);