cBot Errors onTick

Hi,

why this code generate this error:

30/05/2014 13:39:55.054 | System.InvalidOperationException: Obiekt dopuszczający wartość pustą musi mieć wartość.    w System.ThrowHelper.ThrowInvalidOperationException(ExceptionResource resource)    w cAlgo.BreakermindCopyTrader.sendPositions(String Username, String Password)    w cAlgo.BreakermindCopyTrader.OnTick()

        protected override void OnTick()
        {
            // Put your core logic here
            try
            {
                // send all positions
                sendPositions(Username, Password);
                if (Positions.Count >= MaxPositions || Positions.Count == 0)
                {
                    Print("Waiting for You Trader....");
                }
                else
                {

                }

            } catch (Exception e)
            {
                var he = e;
                Print("Waiting for You Trader " + e);
            }

        }

       protected void sendPositions(string Username, string Password)
        {
            // log file path
            string desktopFolder = Environment.GetFolderPath(Environment.SpecialFolder.DesktopDirectory);
            string logPath = Path.Combine(desktopFolder, "MasterLog.db");

            // open position
            var AllPositions = Positions;
            openPositionsString = "[GO]";
            openPips = "|";

            foreach (var position in AllPositions)
            {

                // close with wrong volume
                if (position.Volume < MinVolume)
                {
                    Print("cBot Position: " + position.Id + " Wrong Min Volume (" + MinVolume + ") ");
                    if (position.Volume < MinVolume)
                        ClosePosition(position);
                    Print("cBot Closed Position " + position.Id);
                }

                if (position.StopLoss == null)
                {
                    Print("Position {1} SL price is {0}", position.StopLoss, position.Id);
                }

                if (position.TakeProfit == null)
                {
                    Print("Position {1} TP price is {0}", position.StopLoss, position.Id);
                }

                if (position.StopLoss == null && position.TakeProfit == null)
                {
                    Print("Modifying {0}", position.Id);
                    ModifyPosition(position, GetAbsoluteStopLoss(position, StopLossInPips), GetAbsoluteTakeProfit(position, TakeProfitInPips));

                }

                if (position.StopLoss == null)
                {
                    Print("Modifying {0}", position.Id);
                    //ModifyPosition(position, GetAbsoluteStopLoss(position, StopLossInPips), GetAbsoluteTakeProfit(position, TakeProfitInPips));
                    ModifyPosition(position, GetAbsoluteStopLoss(position, StopLossInPips), position.TakeProfit);
                }

                if (position.TakeProfit == null)
                {
                    Print("Modifying {0}", position.Id);
                    //ModifyPosition(position, GetAbsoluteStopLoss(position, StopLossInPips), GetAbsoluteTakeProfit(position, TakeProfitInPips));
                    ModifyPosition(position, position.StopLoss, GetAbsoluteTakeProfit(position, TakeProfitInPips));
                }

                // BUY positions
                if (position.TradeType == TradeType.Buy && position.Volume >= MinVolume)
                {
                    openPositionsString += position.Id + ";" + position.SymbolCode + ";" + "BUY" + ";" + position.Volume + ";" + position.EntryPrice + ";" + position.StopLoss + ";" + position.TakeProfit + ";" + DateTimeToUnixTimestamp(position.EntryTime) + "|";
                    openPips += position.Pips + "|";
                }

                // SELL positions
                if (position.TradeType == TradeType.Sell && position.Volume >= MinVolume)
                {
                    openPositionsString += position.Id + ";" + position.SymbolCode + ";" + "SELL" + ";" + position.Volume + ";" + position.EntryPrice + ";" + position.StopLoss + ";" + position.TakeProfit + ";" + DateTimeToUnixTimestamp(position.EntryTime) + "|";
                    openPips += position.Pips + "|";
                }

            }
            openPositionsString += "[OG]";
            //================================================================================
            //                                                                    Send request
            //================================================================================

            if (responseFromServer == openPositionsString)
            {
                Print("Same strings ... wait for new Positions !");
                Print("RESPONSE: " + responseFromServer);
                Print("OPEN POS: " + openPositionsString);


            }

            if (responseFromServer != openPositionsString)
            {
                foreach (HistoricalTrade tr in History)
                {
                    // this month closed positions
                    if (DateTime.Now.Month == tr.EntryTime.Month)
                    {
                        //Print("Curr month history positions: " + tr.PositionId + " open time " + tr.EntryTime.Month);
                        closeHistoryPosition += tr.PositionId + "|" + tr.TradeType + "|" + tr.SymbolCode + "|" + tr.Volume + "|" + tr.EntryTime + "|" + tr.EntryPrice + "|" + tr.ClosingTime + "|" + tr.ClosingPrice + "|" + tr.Balance + "###";
                    }
                }
                Print("Position history : " + closeHistoryPosition);
            }


            if (responseFromServer != openPositionsString)
            {

                Print("Send positions...");

                // Account parametrs ============================================
                account = Math.Round(Account.Equity, 2) + "|" + Math.Round(Account.Balance, 2) + "|" + Math.Round(Account.FreeMargin, 2) + "|" + Math.Round(Account.Margin, 2) + "|" + Math.Round((decimal)Account.MarginLevel, 2) + "|" + Account.Currency + "|" + Account.IsLive + "|" + Account.Leverage;


                try
                {
                    using (StreamWriter w = File.AppendText(logPath))
                    {
                        // log request
                        w.WriteLine("REQUEST: " + DateTimeToUnixTimestamp(DateTime.UtcNow) + " : " + openPositionsString);
                        w.Flush();
                        w.Close();
                    }

                    //================================================================================
                    //                   FORCE CERTYFICATE SSL VALIDATION for self signed(openssl) ssl
                    //================================================================================
                    ServicePointManager.ServerCertificateValidationCallback = new System.Net.Security.RemoteCertificateValidationCallback(AcceptAllCertifications);

                    //================================================================================
                    //                                                                      HTTPS POST
                    //================================================================================
                    WebRequest request = WebRequest.Create("https://breakermind.com/set.php");
                    Print("====================================================================================");
                    Print("==>> " + openPositionsString);
                    Print("====================================================================================");
                    byte[] postBytes = Encoding.ASCII.GetBytes("line=" + openPositionsString + "&linepips=" + openPips + "&account=" + account + "&history=" + closeHistoryPosition + "&login=" + Username + "&pass=" + Password);
                    //request.Credentials = CredentialCache.DefaultCredentials;
                    request.Proxy = null;
                    request.Method = "POST";
                    request.ContentType = "application/x-www-form-urlencoded";
                    request.ContentLength = postBytes.Length;
                    Stream requestStream = request.GetRequestStream();
                    requestStream.Write(postBytes, 0, postBytes.Length);
                    HttpWebResponse response = (HttpWebResponse)request.GetResponse();
                    Stream dataStream = response.GetResponseStream();
                    StreamReader reader = new StreamReader(dataStream);
                    responseFromServer = "";
                    responseFromServer = reader.ReadToEnd();

                    openPositionsString = "";

                } catch (Exception e)
                {

                    Print("====================================================================================");
                    Print("Notice: " + e);
                    Print("====================================================================================");
                    using (StreamWriter w = File.AppendText(logPath))
                    {
                        // log response
                        w.WriteLine("ERROR: " + DateTimeToUnixTimestamp(DateTime.UtcNow) + " : " + e);
                        w.Flush();
                        w.Close();
                    }
                }
                Print("====================================================================================");
                Print("<<== " + responseFromServer);
                Print("====================================================================================");

                using (StreamWriter w = File.AppendText(logPath))
                {
                    // log response
                    w.WriteLine("RESPONSE: " + DateTimeToUnixTimestamp(DateTime.UtcNow) + " : " + responseFromServer);
                    w.Flush();
                    w.Close();
                }
            }

        }

Regards