Steps to reproduce:

1. Create a new content item with RichText field
2. Try to insert Facebook (or any other) custom tag into the RichText field
3. On the custom tag attributes screen click the "Cancel" link

Expected result

Insert custom tag dialog is closed.

Actual result

Insert custom tag dialog stays on the screen and the following JavaScript error is thrown:

react-dom.production.min.js:32 Uncaught TypeError: Cannot read property 'setFocused' of null at ButtonCustomTagUpdate.cancelCustomTagEdit