Switching to Monaco Editor broke the app

## Meta info

- Is this a bug or suggestion?: Bug
- Version (click on help icon in footer): 4.0.1
- Context - Web app, Chrome extension or both?: Web app

I was working on a new project in Files Mode, when I decided to try enabling Monaco on a whim. It borked everything, maybe except the editor area. Monaco works, but the current file's tab doesn't appear, and no UI element save for file names in the sidebar are interactive. I cannot open settings to revert back to Codemirror after refreshing the app. I notice in the browser Dev Tools console that there's a message "ReferenceError: monaco is not defined". I've tried this in is Mozilla Firefox, and have not tried replicating this using the Chrome extension.