Installing and configuring the JIRA CKEditor Integration breaks the wysiwyg editor for all non-admin users

Steps to reproduce:

• install the JIRA CKEditor Integration extension
• activate it by adding the config.extraPlugins = 'xwiki-jira-paste' in the editor configuration, in administration
• login with a non-admin user
• go to a page (any page) and click edit, or follow the create form to create a new page

Expected result:

• the rich text editor is loaded for the page edit, or for the content editing of the newly created page

Actual result:

• the editor is not loaded for the page edit - page content remains non-editable and the pointer is indefinitely displayed
  
• the editor is not loaded at all for the creation of a new page
  

This was reproduced on XWiki version 16.10.11, with realtime editor disabled (so it's not related to JIRA-92).