cubicweb #5269544 crash in httpcache / set_headers [open]

2015-04-21 15:23:48 - (cubicweb.web) ERROR: AttributeError("'NoneType' object has no attribute 'timetuple'",)
Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/cubicweb/web/application.py", line 462, in core_handle
    result = controller.publish(rset=rset)
  File "/usr/share/cubicweb/cubes/sentry/views.py", line 26, in publish
    return original_handle(self, rset)
  File "/usr/lib/python2.7/dist-packages/cubicweb/web/views/basecontrollers.py", line 131, in publish
    view.set_http_cache_headers()
  File "/usr/lib/python2.7/dist-packages/cubicweb/web/httpcache.py", line 120, in set_http_cache_headers
    self.http_cache_manager(self).set_headers()
  File "/usr/lib/python2.7/dist-packages/cubicweb/web/httpcache.py", line 84, in set_headers
    req.set_header('Last-modified', mktime(mdate.timetuple()), raw=False)
AttributeError: 'NoneType' object has no attribute 'timetuple'
prioritynormal
typebug
done in<not specified>
load0.500
load left0.500
closed by<not specified>