Unicode error "ascii codec can't encode characters in position 0-1:"

Hello, after writing a task in Greek language and close the program i can't reopen it...
i get the following error:

chris@chris-Aspire-5732Z ~ $ '/opt/extras.ubuntu.com/tickit/bin/tickit'
Using: /home/chris/.local/share/tickit
Traceback (most recent call last):
  File "/opt/extras.ubuntu.com/tickit/tickit/TasksWindow.py", line 327, in ordering_changed_callback
    self._display_tasks(self._last_filter)
  File "/opt/extras.ubuntu.com/tickit/tickit/TasksWindow.py", line 409, in _display_tasks
    if not Task.objects.exists():
  File "/opt/extras.ubuntu.com/tickit/tickit/store.py", line 112, in exists
    self.get_queryset()[0]
  File "/opt/extras.ubuntu.com/tickit/tickit/store.py", line 163, in get_queryset
    return [ self._store._document_to_instance(self._model_class, x) for x in results ]
  File "/opt/extras.ubuntu.com/tickit/tickit/store.py", line 347, in _document_to_instance
    final_data[field.name] = data.content[field.name].decode("utf-8")
  File "/usr/lib/python2.7/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-1: ordinal not in range(128)
Traceback (most recent call last):
  File "/opt/extras.ubuntu.com/tickit/tickit/application.py", line 35, in startup_callback
    self._build_app_menu()
  File "/opt/extras.ubuntu.com/tickit/tickit/application.py", line 54, in _build_app_menu
    self._window = TasksWindow()
  File "/opt/extras.ubuntu.com/tickit/tickit_lib/Window.py", line 48, in __new__
    new_object.finish_initializing(builder)
  File "/opt/extras.ubuntu.com/tickit/tickit/TasksWindow.py", line 216, in finish_initializing
    self._start_task_loading()
  File "/opt/extras.ubuntu.com/tickit/tickit/TasksWindow.py", line 356, in _start_task_loading
    self.active_button_toggled_cb(self.ui.active_button)
  File "/opt/extras.ubuntu.com/tickit/tickit/TasksWindow.py", line 484, in active_button_toggled_cb
    self._display_tasks(PossibleFilters.ACTIVE)
  File "/opt/extras.ubuntu.com/tickit/tickit/TasksWindow.py", line 409, in _display_tasks
    if not Task.objects.exists():
  File "/opt/extras.ubuntu.com/tickit/tickit/store.py", line 112, in exists
    self.get_queryset()[0]
  File "/opt/extras.ubuntu.com/tickit/tickit/store.py", line 163, in get_queryset
    return [ self._store._document_to_instance(self._model_class, x) for x in results ]
  File "/opt/extras.ubuntu.com/tickit/tickit/store.py", line 347, in _document_to_instance
    final_data[field.name] = data.content[field.name].decode("utf-8")
  File "/usr/lib/python2.7/encodings/utf_8.py", line 16, in decode
    return codecs.utf_8_decode(input, errors, True)
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-1: ordinal not in range(128)

i attached the .u1db in case that it's related!