"CKEDITOR Error code: selection-fake-reset" warnings occur in browser console after saving custom tag settings.

Steps:

1. Create e.g. Folder.
2. Add custom tag to e.g. Short description field.
3. Fill all fields and save.
4. Open custom tag settings again.
5. (open browser console) Save.

Actual result: Warnings occur:

[CKEDITOR] Error code: selection-fake-reset.
[CKEDITOR] For more information about this error go to https://ckeditor.com/docs/ckeditor4/latest/guide/dev_errors.html#selection-fake-reset