calendar bug with anonymous user

settings/templatetags/template_filters.py

@@ -115,11 +115,14 @@ def add_month(date, month=1):
 
 @register.filter
 def in_calendar(event, user):
+    if user.is_authenticated():
         if event:
             calendar = user.calendar
             return calendar.check_in_calendar(event)
         else:
             return False
+    else:
+        return False
     """
     types = {'expo':'', 'conf':'', 'seminar':'', 'webinar':''}