[kronolith] delete old horde 4 "system calendar" in horde 5

[Samuel Wolf]

Hi,

I add some calendars in horde 4 as "system calendar" (owned by nobody)  
and share it to my user groups.
Now after upgrade to horde 5 there is no option to modify or delete  
this calendars.

The horde admin user see the calendars in shared calendars and can not  
modifiy it.
How can I modify and delete this calendars?

Samuel