Custom trac query doesn't work when I'm logged in

[Robin]

​http://dev.jquery.com/query

that breaks with an error if I'm logged in:

How to Reproduce

While doing a GET operation on /query, Trac issued an internal error.

(please provide additional details here)

System Information

Trac	0.11dev-r5354
Python	2.3.4 (#1, Oct 11 2006, 06:18:43) [GCC 3.4.6 20060404 (Red Hat 3.4.6-3)]
setuptools	0.6c5
MySQL	server: "5.0.27-log", client: "5.0.27", thread-safe: 0
MySQLdb	1.2.2
Genshi	0.4
Subversion	1.4.3 (r23084)

Python Traceback

Traceback (most recent call last):
  File "/usr/lib/python2.3/site-packages/Trac-0.11dev_r5354-py2.3.egg/trac/web/main.py", line 429, in dispatch_request
    dispatcher.dispatch(req)
  File "/usr/lib/python2.3/site-packages/Trac-0.11dev_r5354-py2.3.egg/trac/web/main.py", line 234, in dispatch
    req.session.save()
  File "/usr/lib/python2.3/site-packages/Trac-0.11dev_r5354-py2.3.egg/trac/web/session.py", line 184, in save
    "VALUES(%s,%s,%s,%s)", attrs)
  File "/usr/lib/python2.3/site-packages/Trac-0.11dev_r5354-py2.3.egg/trac/db/util.py", line 57, in executemany
    return self.cursor.executemany(sql_escape_percent(sql), args)
  File "/usr/lib/python2.3/site-packages/Trac-0.11dev_r5354-py2.3.egg/trac/db/util.py", line 57, in executemany
    return self.cursor.executemany(sql_escape_percent(sql), args)
  File "build/bdist.linux-i686/egg/MySQLdb/cursors.py", line 218, in executemany
  File "build/bdist.linux-i686/egg/MySQLdb/cursors.py", line 312, in _query
  File "build/bdist.linux-i686/egg/MySQLdb/cursors.py", line 276, in _do_query
IntegrityError: (1062, "Duplicate entry 'Robin-1-query_constrain' for key 1")