AttributeError: 'NoneType' object has no attribute 'editor'

[sentry-io]

Sentry Issue: INDIGO-UNEP-7H

AttributeError: 'NoneType' object has no attribute 'editor'
  File "background_task/tasks.py", line 43, in bg_runner
    func(*args, **kwargs)
  File "indigo_app/notifications.py", line 185, in notify_task_action
    notifier.notify_task_action(Action.objects.get(pk=action_id))
  File "indigo_app/notifications.py", line 27, in notify_task_action
    self.send_templated_email('task_assigned', action.target, {
  File "indigo_app/notifications.py", line 146, in send_templated_email
    with override(recipient_user.editor.language):