Exception while changing user configuration

[elibus]

Configuration --> Bug Tracker --> Remove --> OK

raise the following exception:

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bzr: ERROR: exceptions.KeyError: u'bugtracker_trac_gaia_url'

Traceback (most recent call last):
  File "C:/Programmi/Bazaar/plugins\qbzr\lib\config.py", line 470, in do_accept
  File "C:/Programmi/Bazaar/plugins\qbzr\lib\config.py", line 423, in save
  File "bzrlib\util\configobj\configobj.pyo", line 654, in __delitem__
KeyError: u'bugtracker_trac_gaia_url'

bzr 2.0.2 on python 2.5.4 (win32)
arguments: ['bzr', 'qconfig']
encoding: 'cp1252', fsenc: 'mbcs', lang: None
plugins:
  bzrtools C:\Programmi\Bazaar\plugins\bzrtools [2.0.1]
  explorer C:\Programmi\Bazaar\plugins\explorer [0.8.3]
  launchpad C:\Programmi\Bazaar\plugins\launchpad [2.0.2]
  netrc_credential_store C:\Programmi\Bazaar\plugins\netrc_credential_store [2.0.2]
  qbzr C:\Programmi\Bazaar\plugins\qbzr [0.14.5]
  rebase C:\Programmi\Bazaar\plugins\rebase [0.5.4]
  svn C:\Programmi\Bazaar\plugins\svn [1.0.0]
  upload C:\Programmi\Bazaar\plugins\upload [1.0.0dev]
  xmloutput C:\Programmi\Bazaar\plugins\xmloutput [0.8.5]
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