When trying to add at.js I am getting The given range isn't in document.

[cgibsonmm]

I am unable to add at.js and autocomplete to trix when you type in autocomplete field you get a normal return but when you press enter to autocomplete you get "The given range isn't in document." outputted to the console

####Steps to Reproduce####
here is a link to a base rails 5.2.1
https://github.com/cgibsonmm/Trix_at.js_error

1.clone
2.bundle
3.migrate
4.run server
5. try to add @john or @jim to trix form

Details
Trix version:
Browser name and version: chrome
Operating system: mac os

a site live on heroku with the issue
https://trix-at-js.herokuapp.com/