title: Unable to sort using ignoredProperties in Realm
body: <p>I've was trying to sort an <code>RLMResults</code> using an ignored property but I keep getting this error <code>'Invalid sort column', reason: 'Column named '(null)' not found.'</code></p>
  
  <p>This following is my model</p>
  
  <pre><code>class Store: RLMObject {
      dynamic var key = ""
      dynamic var name = ""
      dynamic var latitude = 0.0
      dynamic var longitude = 0.0
      dynamic var distance = 0.0
  
      override class func primaryKey() -&gt; String {
          return "key"
      }
  
      override class func ignoredProperties() -&gt; [AnyObject] {
          return ["distance"]
      }
  }
  </code></pre>
  
  <p>and this is the function that I'm running
  </p>
  
  <pre><code>func sortByDistance(currentLocation: CLLocation) {
      stores = Store.allObjects()
      let realm = RLMRealm.defaultRealm()
  
      realm.transactionWithBlock { [unowned self] in
          for obj in self.stores {
              let store = obj as Store
              let storeLocation = CLLocation(latitude: store.latitude, longitude: store.longitude)
              let distance = currentLocation.distanceFromLocation(storeLocation)
              store.distance = distance
          }
      }
  
      stores = Store.allObjects().sortedResultsUsingProperty("distance", ascending: true)
  }
  </code></pre>
  
  <p>When I tried to do <code>println(stores.firstObject().distance)</code> the default value of <code>0.0</code> gets printed in my console.</p>
  
  <p>Any help will be greatly appreciated.</p>