Duplicated display of the assessment when a user is many groups with access to it

There's a problem when a user belongs to many groups in a site and an assessment is released to some of them. The user will see that assessment repeated, when it should show only once.

Steps to reproduce it:

-Create two groups and add the same student to both.
-Create an assessment published to both groups.
-Login as the student and you'll see the same assessment twice.

Tested at "nightly2.sakaiproject.org:8087/".