cBot allways crashed

I allways get the following message (some hours later after start) :

17/01/2017 11:30:46.828 | c52, EURUSD, h1 | Crashed in OnTick with InvalidOperationException: Nullable object must have a value.

How can I get deeper information about the problem? It would be great if the system tells me the line number where the problem occurs like other programmer languages (Metatrader, c++ etc.)

My OnTick function  simpliest as I can. Where is the problem?

Thanks,

//------------------------------------------------------------------------------------            
        protected override void OnTick()
        {
//------------------------------------------------------------------------------------                    

            if (!bAuth)
            {
                Print("Invalid account!!! EA stopped!");
                Stop();
                return;
            }
            if (bWeekend)
            {
                //  var positions = Positions.FindAll(Label, Symbol);
                //  if (positions.Length > 0)
                ClosePos();
                if (PendingOrders.Count > 0)
                {
                    CloseOrders(TradeType.Buy);
                    CloseOrders(TradeType.Sell);
                }
            }
            else
                WorkWithPositions();

        } //EndTick