AttributeError: NullTranslationsBabel instance has no attribute 'isactive'

[alan]

How to Reproduce

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

(please provide additional details here)

Request parameters:

{'cat_id': None, 'panel_id': None, 'path_info': None}

User agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/44.0.2403.157 Safari/537.36

System Information

Trac	1.0.1
Babel	1.3
Docutils	0.11
Genshi	0.7 (with speedups)
MySQL	server: "5.5.44-0ubuntu0.14.04.1", client: "5.5.44", thread-safe: 1
MySQLdb	1.2.3
Pygments	1.6
Python	2.7.6 (default, Jun 22 2015, 17:58:13) [GCC 4.8.2]
pytz	2012c
setuptools	3.3
jQuery	1.7.2

Enabled Plugins

ComponentDependencyPlugin	0.1
graphviz	0.7.7dev-r13275
GridModify	0.1.6dev-r12235
TicketSidebarProvider	0.0-r11698
TracAccountManager	0.4.4
Tracchildtickets	2.5.3
TracCustomFieldAdmin	0.2.12
TracHoursPlugin	0.6.0dev
TracMasterTickets	4.0.0dev-r14695
TracSumFields	1.0.1
TracWysiwyg	0.12.0.5-r13457
WorkLog	1.0dev-r14737

Python Traceback

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/trac/web/main.py", line 497, in _dispatch_request
    dispatcher.dispatch(req)
  File "/usr/lib/python2.7/dist-packages/trac/web/main.py", line 179, in dispatch
    chosen_handler)
  File "/usr/lib/python2.7/dist-packages/trac/web/main.py", line 325, in _pre_process_request
    chosen_handler = filter_.pre_process_request(req, chosen_handler)
  File "/usr/lib/python2.7/dist-packages/trac/versioncontrol/api.py", line 340, in pre_process_request
    if is_default(reponame):
  File "/usr/lib/python2.7/dist-packages/trac/versioncontrol/api.py", line 34, in is_default
    return not reponame or reponame in ('(default)', _('(default)'))
  File "/usr/lib/python2.7/dist-packages/trac/util/translation.py", line 195, in gettext
    if not self.isactive:
  File "/usr/lib/python2.7/dist-packages/trac/util/translation.py", line 190, in __getattr__
    return getattr(self.active, name)
AttributeError: NullTranslationsBabel instance has no attribute 'isactive'

[Jun Omae]

One of MostFrequentDuplicates.