New Topic button showing when user has no permissions

[ravenlife]

I found another small yet disturbing bug.
It's about the permissions of forums.
When e.g. I disallow the public group to post anything in any forum, they have access to view those forums, but still see the "new topic" button
So the "new topic" button leads to a blank site when someone clicks it, but it's viewable to any group, with and without the permissions to post something.

Greets jxsl