It should only display topics if the inbox is shown.
I have already found a way for this to happen even though the inbox is empty:
After a message which was sent to that group is turned into a public topic.
So:
- Create a new group
- Allow at least admins to message the group
- Add a member to the group to check whether the inbox is shown
- Send a message to the group
- Use the “make public topic” option in the admin wrench menu
- The inbox is empty but even after the database consistency job ran the inbox does not disappear
And in this case the data explorer query above returns that topic