Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.6/hamster/edit_activity.py", line 218, in on_save_button_clicked
    temporary = temporary)
  File "/usr/lib/pymodules/python2.6/hamster/client.py", line 227, in update_fact
    category_name, description, temporary)
  File "/usr/lib/pymodules/python2.6/dbus/proxies.py", line 140, in __call__
    **keywords)
  File "/usr/lib/pymodules/python2.6/dbus/connection.py", line 620, in call_blocking
    message, timeout)
DBusException: org.freedesktop.DBus.Python.TypeError: Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.6/dbus/service.py", line 702, in _message_cb
    retval = candidate_method(self, *args, **keywords)
  File "/usr/lib/pymodules/python2.6/hamster/storage.py", line 156, in UpdateFact
    category_name, description, temporary)
  File "/usr/lib/pymodules/python2.6/hamster/db.py", line 609, in __add_fact
    self.__solve_overlaps(start_time, end_time)
  File "/usr/lib/pymodules/python2.6/hamster/db.py", line 455, in __solve_overlaps
    if start_time < fact["start_time"] and end_time > fact["end_time"]:
TypeError: can't compare datetime.datetime to NoneType