[Bug] Backspace doesn't work correctly in Firefox 78.0a1

Describe a bug.

Steps to reproduce:
1. Go to https://codex.so/editor
2. Place the cursor in the Key features list, after the first bullet
3. Press enter, press backspace
4. Press enter, press backspace again
5. The second time, the line is not removed and the cursor instead jumps to the section header.

Expected behavior: A line is added and removed

Screenshots: http://tkcs.in/5c8a41af39eb

Device, Browser, OS: Firefox 78.0a1 (Nightly)

Editor.js version: Not sure, since this is your main website. :)

Plugins you use with their versions: Once again, this is your website.