Clicking split button returns JavaScript error

Problem/Motivation

Clicking split button returns JavaScript error. Split feature does not work.

Steps to reproduce

This Loom illustrates the workflow
https://www.loom.com/share/08b1e9d71c5b45b1948f33bd718c87d9

1. Add Paragraph that has a text format configuration that includes CKEditor 5 and the split button
2. Add copy
3. Attempt to split the copy
4. Error "Cannot read properties of null (reading 'dispatchEvent')" appears on console.

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes