How to reproduce

• I have a denied group (Les forbans) on the current right context
• I have a user which belongs to this group (Albert), so he appears as denied by it group (ok)
• I add another user (Michel) which belongs to this group => he appears as denied by it group (ok)
• I change the permission of the group to "undefined"

Current behavior

• The user Michel appears as "undefined" (OK)
• The user Albert still appears as denied by its group (KO)

If I do not add another user, the behavior is ok