Error while loading module in Natty

[Adolfo Jayme Barrientos]

This ocurred after a package cleaning and a configuration purging. The traceback is:

Distribution: Ubuntu 11.04 natty
Application: Ubuntu Tweak 0.5.11
Desktop: gnome

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/mainwindow.py", line 502, in setup_notebook
    page = module()
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/modules/compiz.py", line 325, in __init__
    self.create_interface()
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/modules/compiz.py", line 351, in create_interface
    self.launcher_autohide = UnityLauncherAutoHide(_('Make the launcher hide automatically after some time inactive'))
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/modules/compiz.py", line 273, in __init__
    self.plugin = CompizPlugin('unityshell')
  File "/usr/lib/python2.7/dist-packages/ubuntutweak/modules/compiz.py", line 101, in __init__
    self.__plugin = self.context.Plugins[name]
KeyError: 'unityshell'