Error "Object reference not defined for an object instance."

Question

I am developing a Windows service that installs normal, but every time the start, it accuses the following error:

Pcservice Error on: 15/12/2016 10:53:13 Undefined object reference for an object instance.
in Datalayer.Repository.Configrobotrepository.Findbyname(String name) in RSPC.PCService.Scheduleservice() at line 0

I’ve reviewed the code and done several tests, but I can’t understand which object it’s not finding. Follow the codes:

ConfigRobotRepository.FindByName

    public ConfigRobot FindByName(string name)
            {
                using (ISession session = NHibernateHelper.OpenSession())
                {
                    ConfigRobot config = session.CreateCriteria(typeof(ConfigRobot))
                        .Add(Restrictions.Like("Name", name))
                        .UniqueResult<ConfigRobot>();
                    return config;
                }
            }

Scheduleservice()

    try
        {
            foreach (var schedular in schedulars)
            {
                //Get from database mode from this key (example = "PregoeiroChama")
                ConfigRobot config = ConfigRobotController.FindByName(schedular.Key);
                DateTime scheduleTime = DateTime.MinValue;

                if (config.Mode.ToUpper().Equals(ConfigRobotController.Interval))
                {
                    //Get from database interval from this key (example = "PregoeiroChama)
                    int intervalMin = (int)config.IntervalMin;
                    scheduleTime = DateTime.Now.AddMinutes(intervalMin);
                }
                else if (config.Mode.ToUpper().Equals(ConfigRobotController.Daily))
                {
                    //Get from database daily hour from this key (example = "PreogeiroChama")
                    int hour = (int)config.ScheduleTime;

                    if (DateTime.Now.Hour >= hour)
                    {
                        DateTime now = DateTime.Now.AddDays(1);
                        scheduleTime = new DateTime(now.Year, now.Month, now.Day, hour, 0, 0);
                    }
                    else
                        scheduleTime = new DateTime(DateTime.Now.Year, DateTime.Now.Month, DateTime.Now.Day, hour, 0, 0);
                }

                TimeSpan timeSpan = scheduleTime.Subtract(DateTime.Now);

                config.NextDate = scheduleTime;
                config.Status = 'W';

                /*Log*/
                string schedule = string.Format("{0} day(s) {1} hours {2} minutes", timeSpan.Days, timeSpan.Hours, timeSpan.Minutes);
                Log("PCService schedule " + config.Name + " to run after: " + schedule + " {0}", Path.GetTempPath() + config.Name + ".txt");

                long dueTime = Convert.ToInt64(timeSpan.TotalMilliseconds);
                schedular.Value.Change(dueTime, Timeout.Infinite);

                ConfigRobotRepository repo = new ConfigRobotRepository();
                repo.Update(config);
            }
        }
        catch (Exception e)
        {
            System.Diagnostics.StackTrace trace = new System.Diagnostics.StackTrace(e, true);
            var frame = trace.GetFrame(0);
            var line = frame.GetFileLineNumber();
            Log("PCService Error on: {0} " + e.Message + e.StackTrace + " at line " + line, Path.GetTempPath() + "PCService" + ".txt");
            using (var service = new ServiceController("PCService"))
            {
                service.Stop();
            }
        }

What must I do to correct this mistake ?