Error while adding child template to Master Template

     I am getting a Object variable not set error while adding a child template to master template of grid view

here is my code

            {
                grddisplaygrid.DataSource = (DataTable)TransactionController.FetchObject("Itemdetails");
            }

           
           GridViewMultiComboBoxColumn tempmulticombo = (GridViewMultiComboBoxColumn)grddisplaygrid.Columns["BatchNo"];
            tempmulticombo.HeaderText = TransactionController.g_strbatchCaption == "" ? tempmulticombo.HeaderText : TransactionController.g_strbatchCaption;
            tempmulticombo = (GridViewMultiComboBoxColumn)grddisplaygrid.Columns["StockNo"];
            tempmulticombo.HeaderText = TransactionController.g_strStockNoCaption == "" ? tempmulticombo.HeaderText : TransactionController.g_strStockNoCaption;
            GridViewComboBoxColumn tempcombo = (GridViewComboBoxColumn)grddisplaygrid.Columns["SMGUid"];
            tempcombo.IsVisible = false;
            tempcombo = (GridViewComboBoxColumn)grddisplaygrid.Columns["UOM"];
            DataTable dttemp = GetUOmlist();
            tempcombo.DataSource = dttemp;
            tempcombo.DisplayMember = "UnitSymbol";
            tempcombo.ValueMember = "QBGUID";
            tempcombo.DropDownStyle = RadDropDownStyle.DropDownList;
            tempcombo.AutoCompleteMode = AutoCompleteMode.Suggest;
            #region item level Location
            if (TransactionController.g_intLocationenabled == 3)
            {
                tempmulticombo = (GridViewMultiComboBoxColumn)grddisplaygrid.Columns["LocationCd"];
                tempmulticombo.IsVisible = true;
                tempmulticombo.Width = 100;
                tempmulticombo.ReadOnly = false;
                tempmulticombo.HeaderText = TransactionController.g_strlocationCaption == "" ? tempmulticombo.HeaderText : TransactionController.g_strlocationCaption;
            }
            #endregion item level Location

            OverrideColumnVisibility();
            if (TransactionController.g_intDisplayImageinItemDisplaygrid > 0)
            {
                GridViewImageColumn colimage = (GridViewImageColumn)grddisplaygrid.Columns["ItemImage"];
                colimage.IsVisible = true;
            }
            templatesubdetails = new GridViewTemplate();
            templatesubdetails.AllowAddNewRow = false;
            templatesubdetails.AllowEditRow = false;
            templatesubdetails.AllowDeleteRow = false;
            templatesubdetails.ShowRowHeaderColumn = false;
            if (dtsubitemdetails.Columns.Count > 0) { dtsubitemdetails.Columns.Clear(); }
            dtsubitemdetails.Columns.Add("cStockNo", typeof(string));
            dtsubitemdetails.Columns.Add("cItemDesc", typeof(string));
            dtsubitemdetails.Columns.Add("cBatchNo", typeof(string));
            dtsubitemdetails.Columns.Add("cQty", typeof(decimal));
            dtsubitemdetails.Columns.Add("cUOM", typeof(string));
            dtsubitemdetails.Columns.Add("cItemGUID", typeof(string));
            dtsubitemdetails.Columns.Add("cBatchGuid", typeof(string));
            dtsubitemdetails.Columns.Add("cBOMItemGuid", typeof(string));
            dtsubitemdetails.Columns.Add("cRowsrlno", typeof(int));
            dtsubitemdetails.Columns.Add("cBOMQty", typeof(decimal));
            dtsubitemdetails.Columns.Add("BatchEnabled", typeof(int));
            dtsubitemdetails.Rows.Clear();
            templatesubdetails.DataSource = dtsubitemdetails;

            templatesubdetails.Columns["cItemGUID"].IsVisible = false;
            templatesubdetails.Columns["cRowsrlno"].IsVisible = false;
            templatesubdetails.Columns["cBOMQty"].IsVisible = false;
            templatesubdetails.Columns["cBatchGuid"].IsVisible = false;
            templatesubdetails.Columns["cBOMItemGuid"].IsVisible = false;
            templatesubdetails.Columns["BatchEnabled"].IsVisible = false;
            templatesubdetails.Columns["cStockNo"].HeaderText = "Stock No.";
            templatesubdetails.Columns["cStockNo"].Width = 100;
            templatesubdetails.Columns["cItemDesc"].HeaderText = "Description";
            templatesubdetails.Columns["cItemDesc"].Width = 120;

            templatesubdetails.Columns["cBatchNo"].HeaderText = "Batch Number";
            templatesubdetails.Columns["cBatchNo"].Width = 100;
            templatesubdetails.Columns["cBatchNo"].IsVisible = TransactionController.g_intbatchEnabled > 0 ? true : false;

            GridViewDecimalColumn deccolumn = (GridViewDecimalColumn) templatesubdetails.Columns["cQty"];
            deccolumn.HeaderText = "Qty.";
            deccolumn.Width = 70;
            deccolumn.DecimalPlaces = 3;
            deccolumn.FormatString = "{0:N3}";

            templatesubdetails.Columns["cUOM"].HeaderText = "Per";
            templatesubdetails.Columns["cUOM"].Width = 80;
            grddisplaygrid.MasterTemplate.Templates.Clear();
            grddisplaygrid.Relations.Clear();
           
            
           grddisplaygrid.MasterTemplate.Templates.Add(templatesubdetails);

getting the error while executing the above line of code. kindly help me to solve the issue.