Fixed "New ticket" crash when logging out.

[felixxm]

Noticed in Trac's logs:

Traceback (most recent call last):
  File "/home/www/trac/venv/local/lib/python2.7/site-packages/trac/web/main.py", line 280, in dispatch
    self._post_process_request(req)
  File "/home/www/trac/venv/local/lib/python2.7/site-packages/trac/web/main.py", line 480, in _post_process_request
    f.post_process_request(req, *(None,)*extra_arg_count)
  File "/home/www/trac/src/DjangoPlugin/tracdjangoplugin/__init__.py", line 37, in post_process_request
    if req.path_info == '/newticket' and not data.get('preview_mode', False):
AttributeError: 'NoneType' object has no attribute 'get'

[claudep]

👍

[felixxm]

Thanks for checking 👍