Steps to reproduce

1. Open any RichText field in Online Editor
2. Remove all the field content
3. Insert any custom tag
4. Make sure there are no empty paragraphs before and after the inserted custom tag
5. Edit the custom tag
6. Insert a "test" text
7. Make the inserted text a link
8. Chose any location for the link
9. Click the "Save" link button

Expected result

The link within the custom tag is updated.

Actual result

The link is updated, but Online Editor breaks because of the following JavaScript error:

react-dom.production.min.js:61 Uncaught TypeError: Cannot read property 'lastElement' of null

PR is coming