When the theme entry is not configured in trac.ini there is an error raised,
Trac detected an internal error:
TypeError: argument of type 'NoneType' is not iterable
File "/usr/lib/python2.6/dist-packages/trac/web/main.py", line 450, in _dispatch_request
dispatcher.dispatch(req)
File "/usr/lib/python2.6/dist-packages/trac/web/main.py", line 217, in dispatch
self._post_process_request(req, *resp)
File "/usr/lib/python2.6/dist-packages/trac/web/main.py", line 309, in _post_process_request
resp = f.post_process_request(req, *resp)
File "/usr/local/lib/python2.6/dist-packages/TracThemeEngine-2.1.1-py2.6.egg/themeengine/web_ui.py", line 63, in post_process_request
if 'css' in theme:
I attached a quick patch for this. I am still new to python so not sure if this is the best method.