when i use http://localhost:8069/web/database/manager and want to backup the database，an error happened like this

2016-01-27 15:44:41,303 76936 ERROR ? openerp.addons.web.controllers.main: Database.backup

Traceback (most recent call last):

  File "D:\git\odoo9\addons\web\controllers\main.py", line 693, in backup

    ('Content-Disposition', content_disposition(filename)),

  File "D:\git\odoo9\addons\web\controllers\main.py", line 422, in content_disposition

    return request.registry['ir.http'].content_disposition(filename)

TypeError: 'NoneType' object has no attribute '__getitem__'

2016-01-27 15:44:41,839 76936 INFO ? werkzeug: 127.0.0.1 - - [27/Jan/2016 15:44:41] "POST /web/database/backup HTTP/1.1" 200 -