Mercury emulator, Auth ticket error

Hello, RaGEZONE. I have added furnitures etc, everything worked etc, but now later.
Only new users can login, and if a older user login it gets this error:

Bug during user login: System.NullReferenceException: Object reference not set to an instance of an object.
at Mercury.HabboHotel.Items.UserItem..ctor(UInt32 Id, UInt32 BaseItem, String ExtraData, UInt32 Group, String SongCode) in C:\Users\Administrator\Desktop\Mercury v2\HabboHotel\Items\UserItem.cs:line 42
at Mercury.HabboHotel.Users.UserDataManagement.UserDataFactory.GetUserData(String sessionTicket, String ip, Byte& errorCode) in C:\Users\Administrator\Desktop\Mercury v2\HabboHotel\Users\UserDataManagement\UserDataFactory.cs:line 220
at Mercury.HabboHotel.GameClients.GameClient.tryLogin(String AuthTicket) in C:\Users\Administrator\Desktop\Mercury v2\HabboHotel\GameClients\GameClient.cs:line 158