title: Trouble with a git bare repository after upgrading trac from 0.11 to 0.12
body: <p>I just recently upgraded my Trac system so we could handle multiple repositories. I started getting some browser errors and tracked it down to GitPlugin (when I disable it all of the errors go away, though of course my version control tracking does too).</p>
  
  <p>On every page I get:</p>
  
  <pre><code>'Warning:  Error with navigation contributor "BrowserModule"'
  </code></pre>
  
  <p>and on the timeline page I get:</p>
  
  <pre><code> Trac detected an internal error:
  
  TypeError: 'NoneType' object is unsubscriptable
  </code></pre>
  
  <p>The Log gives me this for the timeline page out of 'main':</p>
  
  <pre><code>Internal Server Error: Traceback (most recent call last): File "/usr/local
  /lib/python2.6/dist-packages/Trac-0.12-py2.6.egg/trac/web/main.py", line 513, in 
  _dispatch_request dispatcher.dispatch(req) File "/usr/local/lib/python2.6/dist-packages
  /Trac-0.12-py2.6.egg/trac/web/main.py", line 235, in dispatch resp = 
  chosen_handler.process_request(req) File "/usr/local/lib/python2.6/dist-packages/Trac-
  0.12-py2.6.egg/trac/timeline/web_ui.py", line 142, in process_request available_filters += 
  event_provider.get_timeline_filters(req) or [] File "/usr/local/lib/python2.6/dist-packages
  /Trac-0.12-py2.6.egg/trac/versioncontrol/web_ui/changeset.py", line 861, in 
  get_timeline_filters repositories = rm.get_real_repositories() File "/usr/local
  /lib/python2.6/dist-packages/Trac-0.12-py2.6.egg/trac/versioncontrol/api.py", line 588, in 
  get_real_repositories repos = self.get_repository(reponame) File "/usr/local/lib/python2.6
  /dist-packages/Trac-0.12-py2.6.egg/trac/versioncontrol/api.py", line 526, in 
  get_repository repos = connector.get_repository(rtype, rdir, repoinfo.copy()) File 
  "/usr/lib/python2.6/dist-packages/tracext/git/git_fs.py", line 159, in get_repository 
  shortrev_len=self._shortrev_len) File "/usr/lib/python2.6/dist-packages/tracext
  /git/git_fs.py", line 177, in __init__ Repository.__init__(self, "git:"+path, None, log)
   File "/usr/local/lib/python2.6/dist-packages/Trac-0.12-py2.6.egg/trac/versioncontrol
  /api.py", line 730, in __init__ self.reponame = params['name'] TypeError: 'NoneType' 
  object is unsubscriptable
  </code></pre>
  
  <p>and this for all pages out of 'Chrome':</p>
  
  <pre><code>Error with navigation contributor BrowserModule: TypeError: 'NoneType' object is unsubscriptable
  </code></pre>
  
  <p>I set up a few test environments before upgrading this system and they both worked with multi repositories and git, but with 2 key differences: they started as 0.12 and the repositories are not bare repositories. </p>
  
  <p>My question is this: Did I mess something up when upgrading and need to start from a fresh environment, do I need to switch my repositories to non-bare, or am I missing something completely and need to do something else?</p>