traceback when undoing a trim

[Jeff Fortin Tam]

With jokosher trunk:

Traceback (most recent call last):
  File "/home/jeff/trunks/jokosher/Jokosher/JokosherApp.py", line 921, in OnUndo
    self.project.Undo()
  File "/home/jeff/trunks/jokosher/Jokosher/Project.py", line 944, in Undo
    self.ExecuteAction(cmd)
  File "/home/jeff/trunks/jokosher/Jokosher/Project.py", line 1085, in ExecuteAction
    getattr(target_object, cmdList[1])(_undoAction_=newUndoAction, *cmdList[2])
  File "/home/jeff/trunks/jokosher/Jokosher/UndoSystem.py", line 78, in UndoWrapper
    result = func(funcSelf, *args, **kwargs)
  File "/home/jeff/trunks/jokosher/Jokosher/Event.py", line 504, in JoinEvent
    self.levels_list = LevelsList.add(old_duration, joinEvent.levels_list, self.levels_list)
TypeError: add() takes exactly 2 arguments (3 given)