Change redirect behaviour if you navigate to a forbidden page

[Elblinator]

Current behavior
If you try to navigate to a page which you are not allowed to see, then you are directly redirected to the "You are not supposed to be here" page.

Wanted behavior
If you try to navigate to a page which you are not supposed to see then you should be automatically directed to the dashboard.
One exception:
If a user is only allowed to see one single meeting then the user should be redirected to the dashboard and then to this meeting. The redirect from the dashboard to the single meeting is already implemented, you just have to make sure that it still works afterwards.