Broken with trix editor

[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/