If a canonical route is a form, the iframe previewer makes the form inaccessible

[oknate]

Package containing the bug

I’m not sure

Describe the bug

If you add a next entity type config for an entity such as redirect, the iframe preview takes over edit form, which is at the canonical route.

Expected behavior

It should not replace the form, if the canonical route is a form.

Steps to reproduce:

1. First '...'
2. Then '....'
3. 😢

Additional context

Add any other context about the problem here.