while referencing an indicator: Crashed in OnTick with NullReferenceException: Object reference not set to an instance of an object.

Dear all,

I got an behavior I can't explain:

I'm referencing an indicator. Referenced indicator works without compiling or runtime error. If I run the referecing indicator, the correct values from the referenced indicator are displayed (good!) BUT the log throughs out "Crashed in ... with NullReferenceException: Object reference not set to an instance of an object." on every tick (?).

I have no idea why this happens. If I reference another indicator, everything works fine without any error messages. Both indicators are referenced in the "manage Reference" section. Both indicators work fine without any errors for itself.

Any idea where to look or what might going wrong?

Kindest regards,

here the referencing (receiving) indicator:

using System;
using cAlgo.API;
using cAlgo.API.Internals;
using cAlgo.API.Indicators;
using cAlgo.Indicators;

namespace cAlgo
{

    [Indicator(IsOverlay = false, TimeZone = TimeZones.UTC, AutoRescale = false, AccessRights = AccessRights.None)]
    public class SampleReferenceincludecustomIndicatorVolume : Indicator
    {
        [Parameter("Source")]
        public DataSeries DataSource { get; set; }

        [Output("Referenced DOSC Output", LineColor = "Red", PlotType = PlotType.Points)]
        public IndicatorDataSeries refDOSC { get; set; }

        [Output("ZeroLine", LineColor = "White")]
        public IndicatorDataSeries zeroline { get; set; }



        public DOSC _isTradeAllowed;
        public EXITRVINNFX _isTradeAllowed1;


        protected override void Initialize()
        {

            //_isTradeAllowed = Indicators.GetIndicator<DOSC>(DataSource, 7, 1);
            _isTradeAllowed1 = Indicators.GetIndicator<EXITRVINNFX>(DataSource, 10);
        }

        public override void Calculate(int index)
        {
            //refDOSC[index] = _isTradeAllowed.Result[index];
            refDOSC[index] = _isTradeAllowed1._rviBool[index];
            zeroline[index] = 0;


        }
    }
}

and here the referenced (sending) indicator:

using System;
using cAlgo.API;
using cAlgo.API.Indicators;
using cAlgo.API.Internals;
using cAlgo.Indicators;
using System.Threading;

namespace cAlgo.Indicators
{
    [Indicator(IsOverlay = false, ScalePrecision = 5, AccessRights = AccessRights.None)]
    public class EXITRVINNFX : Indicator
    {
        [Parameter("Source")]
        public DataSeries Source { get; set; }

        [Parameter(DefaultValue = 10)]
        public int Period { get; set; }

        [Output("RVI", LineColor = "Green")]
        public IndicatorDataSeries _rviResult { get; set; }

        [Output("Signal", LineColor = "Red")]
        public IndicatorDataSeries _rviSignal { get; set; }

        [Output("Bool", LineColor = "Red", PlotType = PlotType.Points)]
        public IndicatorDataSeries _rviBool { get; set; }


        private IndicatorDataSeries _value1;
        private IndicatorDataSeries _value2;
        private string _text;
        private Color _color;



        protected override void Initialize()
        {
            _value1 = CreateDataSeries();
            _value2 = CreateDataSeries();
            _text = "";
            _color = Color.Red;
        }


        public override void Calculate(int index)
        {
            _value1[index] = ((Bars.ClosePrices[index] - Bars.OpenPrices[index]) + 2 * (Bars.ClosePrices[index - 1] - Bars.OpenPrices[index - 1]) + 2 * (Bars.ClosePrices[index - 2] - Bars.OpenPrices[index - 2]) + (Bars.ClosePrices[index - 3] - Bars.OpenPrices[index - 3])) / 6;

            _value2[index] = ((Bars.HighPrices[index] - Bars.LowPrices[index]) + 2 * (Bars.HighPrices[index - 1] - Bars.LowPrices[index - 1]) + 2 * (Bars.HighPrices[index - 2] - Bars.LowPrices[index - 2]) + (Bars.HighPrices[index - 3] - Bars.LowPrices[index - 3])) / 6;

            double num = 0;
            double denum = 0;
            for (int i = 0; i < Period; i++)
            {
                num += _value1[index - i];
                denum += _value2[index - i];
            }

            _rviResult[index] = num / denum;

            _rviSignal[index] = (_rviResult[index] + 2 * _rviResult[index - 1] + 2 * _rviResult[index - 2] + _rviResult[index - 3]) / 6;




            if (_rviSignal.HasCrossedAbove(_rviResult, 0))
            {

                _text = "EXIT long" + _rviBool.LastValue;
                _color = Color.Red;
                _rviBool[index] = 1;

            }
            else
            {

                if (_rviResult.HasCrossedAbove(_rviSignal, 0))
                {
                    _text = "EXIT short" + _rviBool.LastValue;
                    _color = Color.Red;
                    _rviBool[index] = -1;
                }
                else
                {
                    _text = "";
                    _rviBool[index] = 0;
                }
            }
            IndicatorArea.DrawStaticText("Symbols", _text, VerticalAlignment.Top, HorizontalAlignment.Right, _color);

        }

    }
}