title: Mongodb error : Can't extract geo keys from object, malformed geometry?
body: <p>I get the following error with mongodb 2.4.3</p>
  
  <p><code>Can't extract geo keys from object, malformed geometry?</code></p>
  
  <pre><code>{type: "Polygon",
  coordinates: [
      [
          [
              103.8324334524412,
              1.284232321447769
          ],
          [
              103.8342325475588,
              1.284232321447769
          ],
          [
              103.8342325469261,
              1.282433678236006
          ],
          [
              103.8324334530738,
              1.282433678236006
          ]
      ]
  ]}
  </code></pre>
  
  <p>Can someone help me understand the problem? it looks like a valid geoJSON object. My index is of type <code>2dsphere</code>.</p>
  
  <p>The two steps i am running are :</p>
  
  <pre><code>collection.ensureIndex {'geometry' : "2dsphere"}, (error) =&gt;
    # some error checking
    # and then
    collection.insert features, (error) =&gt;
      # features is an array of geoJSON feature objects
      # {"type" : "Feature"
      #  "geometry" : &lt;the Polygon object above&gt;
        }
  </code></pre>
  
  <p>The insert query gives this error.
  The complete document i am trying to insert is:</p>
  
  <pre><code>{
      "type":"Feature",
      "geometry": {
          "type":"Polygon",
          "coordinates":[
             [
               [103.83243345244122,1.2842323214477689],
               [103.83423254755876,1.2842323214477689],
               [103.83423254692615,1.2824336782360055],
               [103.83243345307383,1.2824336782360055]
             ]
          ]
        },
      "properties":{"name" : "My location"}
    }
  </code></pre>