Fatal error when adding component after force deleting JS code component config

Overview

After placing a JS code component on a page, if you force-delete its config entity using Drush, subsequent attempts to add any component in the Canvas UI result in a fatal error:

An unexpected error has occurred while fetching the layout.
Error 500: assert($source instanceof ComponentSourceInterface)

This prevents further editing or use of the Canvas page after such a deletion.

Steps to Reproduce

1. Place a JS code component on a page.
2. Force-delete its config entity via Drush:
   
   drush config:delete xb_javascript_component.COMPONENT_ID
3. Reload the page in the Canvas UI.
4. Attempt to add any component to the page.
5. Observe the error:
   
   

   An unexpected error has occurred while fetching the layout.
   Error 500: assert($source instanceof ComponentSourceInterface)
       

Proposed resolution

User interface changes