title: OneToOneField empty from both sides
body: <p>is there any way to create a OneToOneField, which can be empty on both sides?</p>
  
  <p>I mean if i' ve this relation between <code>ModelA</code> and <code>ModelB</code>, i want to allow <code>ModelA</code> not having a <code>ModelB</code> relatioship, and <code>ModelB</code> not having a <code>ModelA</code> relationship.</p>
  
  <p>In my example there' s this code:</p>
  
  <p><code>class Forum(models.Model):<BR>
      .....<BR>
  <BR>
  class Jobs(models.Model):<BR>
      forum = models.OneToOneField(Forum, blank = True, null = True)
  </code></p>
  
  <p>. This works pretty well from <code>Jobs -> Forum</code> direction, but when i try it from <code>Forum -> Jobs</code> direction, certainly i get <code>query does not exist</code> error.</p>
  
  <p>As a workaround i could use <code>ManyToManyField</code> or <code>hasattr</code> to check it, but i' d be interested rather in a OneToOneField like solution.</p>
  
  <p>Thanks.</p>