TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

[muthu]

How to Reproduce

While doing a POST operation on /admin/general/svnpolicies, Trac issued an internal error.

(please provide additional details here)

Request parameters:

{'__FORM_TOKEN': u'0e95d8fe9dc12f82ebfad91e',
 'advanced_postcomit_content': u'',
 'advanced_precomit_content': u'',
 'cat_id': u'general',
 'commands.enabled': u'true',
 'email.attachment': u'true',
 'email.attachment_limit': u'10000',
 'email.enabled': u'true',
 'email.list': u'muthu.kumar@msys-tech.com',
 'email.prefix': u'ACS',
 'email_from_address': u'',
 'email_subject_cx': u'true',
 'log_message.minimum': u'3',
 'log_message.pattern': u'',
 'panel_id': u'svnpolicies',
 'path_info': None,
 'svn_property': u'true',
 'svnpolicies_enabled': u'true'}

System Information

Trac	0.11.7
Python	2.6.5 (r265:79063, Apr 16 2010, 13:09:56) [GCC 4.4.3]
setuptools	0.6
MySQL	server: "5.1.41-3ubuntu12.10", client: "5.1.41", thread-safe: 1
MySQLdb	1.2.2
Genshi	0.5.1
Agilo	0.9.3
Pygments	1.2.2

Python Traceback

Traceback (most recent call last):
  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 206, in dispatch
    resp = chosen_handler.process_request(req)
  File "/usr/lib/python2.6/dist-packages/trac/admin/web_ui.py", line 114, in process_request
    path_info)
  File "/usr/local/lib/python2.6/dist-packages/TracSVNPoliciesPlugin-0.2-py2.6.egg/svnpolicies/admin.py", line 189, in render_admin_panel
    self._process_new_settings(req)
  File "/usr/local/lib/python2.6/dist-packages/TracSVNPoliciesPlugin-0.2-py2.6.egg/svnpolicies/admin.py", line 255, in _process_new_settings
    self._delete_hook_links('pre-commit')
  File "/usr/local/lib/python2.6/dist-packages/TracSVNPoliciesPlugin-0.2-py2.6.egg/svnpolicies/admin.py", line 529, in _delete_hook_links
    svn_hook= svn_repository + os.path.sep + link_name
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

[Remy Blank]

Duplicate of #10084.