fixes #762 - Marking unwatched doesn't update display

MediaBrowser.Controller/Entities/UserRootFolder.cs

@@ -1,4 +1,5 @@
 using MediaBrowser.Controller.Providers;
+using MediaBrowser.Model.Dto;
 using System;
 using System.Collections.Generic;
 using System.Linq;
@@ -51,5 +52,10 @@ namespace MediaBrowser.Controller.Entities
                 LibraryManager.RegisterItem(item);
             }
         }
+
+        public override void FillUserDataDtoValues(UserItemDataDto dto, UserItemData userData, User user)
+        {
+            // Nothing meaninful here and will only waste resources
+        }
     }
 }