Steps to reproduce:

• Prepare a test eZ Studio installation (studio-clean), clean. For issue reproduction purposes, no settings change is required, just use the default;
• Login to the admin interface, go to Admin Panel/Languages, and create a new language e.g. "en";
• Do not add the new language to the app/config/ezplatform.yml configurations;
• Go to Content/Content structure, and create a new article in the new language;
• Publish. The article is published, but a "Cannot read property '_href' of undefined" error message is displayed at the bottom.

Note: that error message is displayed every time the content is accessed in the content tree.