Handle redirect to designer after lost authentication

When a deployment is happening and you try to access designer, you can end up being redirected by CAS to connect.nuxeo.com/nuxeo/designer

Problem is the UI loads only partially (you're not in a project) and it's hard to understand why if you don't have knowledge about how designer works.

Expected:

• When I am accessing such an invalid URL, redirect me to a valid page
• or don't take me to an invalid URL in the first place