[Dashboard] Properties panel fails to load when resources don't exist

[diehbria]

this task is to make it so the properties panel always loads - even when there are assets referenced within it that do not exist.

The current implementation results in the following user experience - such that if there's a single property that no longer exists, the entire widget is unusable. This is demonstrated in the screenshot below

- [ ] Property panel works and allows you to edit widgets when there are unfound assets
- [ ] Tests in place to prevent regression