Blueprints are broken when the name of a field in the schema changes

Steps to reproduce

npm run start:firefox
Click "Import Blog Posts"
Navigate to the screen where one clicks around to fill the blogpost
Select the title of the post
In your editor, rename the title field in ./schema/subjects/blog-post.json to something other than title. Note that it's fields.title we're modifying, not the top-level title.
In your terminal, do npm run build:schema
In your editor, add some blank lines in a TypeScript file and save it, so that the extension reloads
The following error is displayed

Unexpected Application Error!
field is undefined

SingleFieldEditor@moz-extension://1c528d92-66fa-4917-afc2-4888dbede0f5/app.js:375190:1212