calendar bug with anonymous user

settings/templatetags/template_filters.py

@@ -115,9 +115,12 @@ def add_month(date, month=1):
 
 @register.filter
 def in_calendar(event, user):
-    if event:
+    if user.is_authenticated():
-        calendar = user.calendar
+        if event:
-        return calendar.check_in_calendar(event)
+            calendar = user.calendar
+            return calendar.check_in_calendar(event)
+        else:
+            return False
     else:
         return False
     """