title: Check if OneToOneField is None in Django
body: <p>I have two models like this:</p>
  
  <pre><code>class Type1Profile(models.Model):
      user = models.OneToOneField(User, unique=True)
      ...
  
  
  class Type2Profile(models.Model):
      user = models.OneToOneField(User, unique=True)
      ...
  </code></pre>
  
  <p>I need to do something if the user has Type1 or Type2 profile:</p>
  
  <pre><code>if request.user.type1profile != None:
      # do something
  elif request.user.type2profile != None:
      # do something else
  else:
      # do something else
  </code></pre>
  
  <p>But, for users that don't have either type1 or type2 profiles, executing code like that produces the following error:</p>
  
  <pre><code>Type1Profile matching query does not exist.
  </code></pre>
  
  <p>How can I check the type of profile a user has?</p>
  
  <p>Thanks</p>