calendar menu should not be showed in private groups if you are not a member

Hi!

I found that if you are browsing the groups directory, and click in a private group where you're not member, you can still view the 'calendar' link on the group menu (not the content, true, but you can see the calendar link).

I think that is not correct, when you're not a member you cant view any of the private group options (wire, forum, ... other group modules). So the correct way is to hide the calendar link too.

Best regards.