C# - NullReferenceException - В экземпляре объекта не задана ссылка на объект

    public partial class DateTimePanel : UserControl {
        // vars
        private int curTime;
        
        public int getTime {
            get { return curTime; }
        }
        public DateTime getDate {
            get { return DateTime.Now; }
        }
        
        // events
        public event SelectDateEventHandler SelectDate;
        public event TickTimerEventHandler TickTimer;
 
        protected virtual void OnSelectDate(SelectDateEventArgs e) {
            SelectDate(this, e);
        }
        
        protected virtual void OnTickTimer(TickTimerEventArgs e) {
            TickTimer(this, e);
        }
        //
 
        public DateTimePanel() {
            InitializeComponent();
        }
 
        public bool setTimer(bool en) {
            curTime = -1;
            mainTimer.Enabled = en;
            return mainTimer.Enabled;
        }
 
        private void calendar_DateSelected(object sender, DateRangeEventArgs e) {
            OnSelectDate(new SelectDateEventArgs(e.Start));
        }
 
        private void mainTimer_Tick(object sender, EventArgs e) {
            int H, M, time;
            string strtime;
                   
            strtime = DateTime.Now.ToLongTimeString();
            H = Int32.Parse(strtime.Substring(0, 2));
            M = Int32.Parse(strtime.Substring(3, 2));
            time = H * 60 + M;
            if (curTime != time) {
                curTime = time;
                OnTickTimer(new TickTimerEventArgs(time));
            }
 
            dateLbl.Text = DateTime.Now.ToLongDateString();
            timeLbl.Text = strtime;
        }
    }
 
    public delegate void SelectDateEventHandler(object sender, SelectDateEventArgs e);
    public delegate void TickTimerEventHandler(object sender, TickTimerEventArgs e);
 
    public class SelectDateEventArgs : EventArgs {
        private DateTime date;
        public SelectDateEventArgs(DateTime date) {
            this.date = date;
        }
        public DateTime SelectedDate {
            get { return date; }
        }
    }
    public class TickTimerEventArgs : EventArgs {
        private int time;
        public TickTimerEventArgs(int time) {
            this.time = time;
        }
        public int getTime {
            get { return time; }
        }
    }
 
}

protected virtual void OnSelectDate(SelectDateEventArgs e) {
            SelectDate(this, e);
        }

protected virtual void OnTickTimer(TickTimerEventArgs e) {
            TickTimer(this, e);
        }