title: Mongodb NULL Instead of delete
body: <p>I managed to found out how to delete field but I have a problem It doesn't really delete it it just set it to NULL.</p>
  
  <pre><code>db.user.update({'username': 'mezo', 'person': {'$in' : ['masidnadi241479214']}}, {'$unset': {'person.$': 1}})
  </code></pre>
  
  <p>My structure is something like that:</p>
  
  <pre><code>{
      "_id" : ObjectId("4ff14c7461d69af811000000"),
      "confirmed" : true,
      "person" : [
              null,
              null,
              "194724198274192",
              "3"
      ],
      "username" : "mezo"
  </code></pre>
  
  <p>}</p>