TypeError: cannot concatenate 'str' and 'NoneType' objects

[asaraiva]

How to Reproduce

While doing a POST operation on /admin/ganttcalendar/holiday, Trac issued an internal error.

(please provide additional details here)

Request parameters:

{'__FORM_TOKEN': u'd2635d76eedf468ea8e8345b',
 'cat_id': u'ganttcalendar',
 'create_table': u'Create table and insert some holidays.',
 'panel_id': u'holiday',
 'path_info': None}

User agent: Mozilla/5.0 (Windows NT 6.1) AppleWebKit/534.30 (KHTML, like Gecko) Chrome/12.0.742.112 Safari/534.30

System Information

Trac	0.12
Genshi	0.6
mod_python	3.2.8
pysqlite	2.3.3
Python	2.4.3 (#1, Sep 3 2009, 15:37:37) [GCC 4.1.2 20080704 (Red Hat 4.1.2-46)]
setuptools	0.6c7
SQLite	3.3.6
Subversion	1.6.13 (r1002816)
jQuery	1.4.2

Enabled Plugins

TracGanttCalendarPlugin

0.6.2

Python Traceback

Traceback (most recent call last):
  File "/usr/lib/python2.4/site-packages/trac/web/main.py", line 513, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/lib/python2.4/site-packages/trac/web/main.py", line 235, in dispatch
    resp = chosen_handler.process_request(req)
  File "/usr/lib/python2.4/site-packages/trac/admin/web_ui.py", line 116, in process_request
    path_info)
  File "build/bdist.linux-x86_64/egg/ganttcalendar/admin.py", line 76, in render_admin_panel
TypeError: cannot concatenate 'str' and 'NoneType' objects

[Remy Blank]

PluginIssue (ganttcalendar).