Discovered while testing MDLQA-17371.

While using TinyMCE editor, an error occurs when you insert an image.

Steps to reproduce:

1. Go to Site Administration > Plugins > Text Editors > Manage Editors
2. Enable TinyMCE editor and set it as the default editor
3. Go to user profile and click Edit profile
4. Open browser console
5. Insert an image
   1. Insert > Image
   2. Image icon in toolbar
6. Observe console, an error occurs