ubuntu-tweak crashed when opened tab "Advanced Powermanager settings"

Please give the Error Message to here, so that I can know what's the problem.

Ubuntu 9.10 Karmic - Error Message:

Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.6/ubuntutweak/mainwindow.py", line 393, in setup_notebook
    page = module()
  File "/usr/lib/pymodules/python2.6/ubuntutweak/modules/powermanager.py", line 50, in __init__
    min=0, max=100, digits=0),
  File "/usr/lib/pymodules/python2.6/ubuntutweak/common/factory.py", line 49, in create
    return getattr(cls, 'do_composite_create')(widget, **kwargs)
  File "/usr/lib/pymodules/python2.6/ubuntutweak/common/factory.py", line 60, in do_composite_create
    new_widget = globals().get(widget)(**kwargs)
  File "/usr/lib/pymodules/python2.6/ubuntutweak/widgets/widgets.py", line 143, in __init__
    self.set_value(self.__setting.get_value())
  File "/usr/lib/pymodules/python2.6/ubuntutweak/conf/gconfsetting.py", line 88, in get_value
    return self.__type(None)
TypeError: int() argument must be a string or a number, not 'NoneType'

Hope it helps