title: Get objects with date greater than today or empty date
body: <p>I need to select all model objects with date field greater than today date OR date field empty.</p>
  
  <p>I have following code:</p>
  
  <pre><code>@login_required
  def event_new(request, person_uuid=None):
      today = datetime.datetime.today()
      #valid_until may be empty
      profile = Profile.objects.filter(company=request.user.company, valid_until__gte=today)
  </code></pre>
  
  <p>I need to select all Profile objects with valid_until field empty or (if set) greater than today. How can I achieve this?</p>