public-form view throws exception if the form-config does not exist locally

[tomwwinter]

Describe the bug
When a user open a public form with an id that does not exist in the local database, an unhandled exception is thrown.

To Reproduce
Start application locally

1. Go to some non existing public-form: http://localhost:4200/public-form/123f
2. See error

Expected behavior
We should handle all errors and show a 404 error page.

Screenshots

Desktop (please complete the following information):

• OS: all
• Browser: all
• Version: 3.42.2

Additional context
Add any other context about the problem here.