add ignore attribute

MediaBrowser.Controller/Entities/CollectionFolder.cs

@@ -188,6 +188,7 @@ namespace MediaBrowser.Controller.Entities
         /// Our children are actually just references to the ones in the physical root...
         /// </summary>
         /// <value>The actual children.</value>
+        [IgnoreDataMember]
         protected override IEnumerable<BaseItem> ActualChildren
         {
             get { return GetActualChildren(); }