System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> NHibernate.Exceptions.GenericADOException: could not insert: [Helpmebot.Model.User][SQL: INSERT INTO user (mask, account, user_lastmodified) VALUES (?, ?, ?)] ---> MySql.Data.MySqlClient.MySqlException: Column 'mask' cannot be null