[algorithms] Visiting usable algorithms causes a crash on the BEAT web server

Exception text:

Traceback:

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  149.                     response = self.process_exception_by_middleware(e, request)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/core/handlers/base.py" in get_response
  147.                     response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/remote/sw/beat.web/src/beat.web/beat/web/algorithms/views.py" in view
  226.                               context_instance=RequestContext(request))

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/shortcuts.py" in render_to_response
  45.             using=using)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/loader.py" in render_to_string
  114.                         template_name, context, context_instance, dirs, dictionary)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/engine.py" in render_to_string
  244.             return t.render(context_instance)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/base.py" in render
  206.                     return self._render(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/base.py" in _render
  197.         return self.nodelist.render(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/base.py" in render
  992.                 bit = node.render_annotated(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/base.py" in render_annotated
  959.             return self.render(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/loader_tags.py" in render
  173.         return compiled_parent._render(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/base.py" in _render
  197.         return self.nodelist.render(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/base.py" in render
  992.                 bit = node.render_annotated(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/base.py" in render_annotated
  959.             return self.render(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/loader_tags.py" in render
  69.                 result = block.nodelist.render(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/base.py" in render
  992.                 bit = node.render_annotated(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/base.py" in render_annotated
  959.             return self.render(context)

File "/remote/sw/beat.env.web-1.1.0/usr/lib/python2.7/site-packages/django/template/library.py" in render
  223.         _dict = self.func(*resolved_args, **resolved_kwargs)

File "/remote/sw/beat.web/src/beat.web/beat/web/ui/templatetags/ui_tags.py" in history
  212.              'history': obj.json_history(context['request'].user),

File "/remote/sw/beat.web/src/beat.web/beat/web/common/models.py" in json_history
  503.         return simplejson.dumps(self.api_history(for_user))

File "/remote/sw/beat.web/src/beat.web/beat/web/common/models.py" in api_history
  497.         return _recurse(self.history(for_user))

File "/remote/sw/beat.web/src/beat.web/beat/web/common/models.py" in _recurse
  489.             o = d['object']

Exception Type: TypeError at /platform/algorithms/chichan/enroll_by_comp_averaging/23/
Exception Value: 'NoneType' object has no attribute '__getitem__'