Saving fails for Qualified for final exams

[torgeirl]

It seems #1230 introduced an error preventing administrators from saving Qualified for final exams:

KeyError: 'plugindata'
  File "django/core/handlers/base.py", line 197, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "cradmin_legacy/crapp.py", line 86, in viewwrapper
    return has_access_to_cradmin_instance(cradminview(view))(request, *args, **kwargs)
  File "cradmin_legacy/decorators.py", line 32, in wrapper
    return view_function(request, *args, **kwargs)
  File "cradmin_legacy/decorators.py", line 70, in wrapper
    response = view_function(request, *args, **kwargs)
  File "django/views/generic/base.py", line 104, in view
    return self.dispatch(request, *args, **kwargs)
  File "devilry/devilry_qualifiesforexam/views/qualification_preview_view.py", line 112, in dispatch
    return super(QualificationPreviewView, self).dispatch(request, *args, **kwargs)
  File "django/views/generic/base.py", line 143, in dispatch
    return handler(request, *args, **kwargs)
  File "django/views/generic/edit.py", line 153, in post
    return self.form_valid(form)
  File "devilry/devilry_qualifiesforexam/views/qualification_preview_view.py", line 164, in form_valid
    if self.request.session['plugindata']:
  File "django/contrib/sessions/backends/base.py", line 53, in __getitem__
    return self._session[key]

[torgeirl]

Solved in ff480e7e7375ddc6ab4d2a579b486700f571cc0f (v6.2.1)