Opening group activity, you're not allowed to view, in a new tab leads to broken site

Navigating the Discourse Labyrinth: When New Tabs Lead to Broken Paths

I couldn’t resist sharing the AI-generated title

I think this is still a problem. It happened not only at the broken mentions view but affects at least all group activity pages when you are not allowed to view the group’s members.
To reproduce, open Group of users testing the new-new functionality - Discourse Meta in a new tab (users who are allowed to see the members of that group need to check without being logged in)

As you can see most things are broken when you visit that link. You cannot login or choose a different theme.