Call stack:
Telerik.WinControls.GridView.dll!Telerik.WinControls.UI.GridGroupHeaderRowElement.Initialize(Telerik.WinControls.UI.GridViewRowInfo rowInfo) Line 100 at Telerik.WinControls.UI\GridGroupHeaderRowElement.cs(100) Telerik.WinControls.GridView.dll!Telerik.WinControls.Export.GridExportUtils.GetRowHeight(Telerik.WinControls.UI.RadGridView radGridView, Telerik.WinControls.UI.RowElementProvider rowProvider, Telerik.WinControls.UI.CellElementProvider cellProvider, Telerik.WinControls.UI.GridViewRowInfo gridViewRowInfo, bool exportVisualSettings) Line 158 at Telerik.WinControls.Export\GridExportUtils.cs(158) Telerik.WinControls.GridView.dll!Telerik.WinControls.Export.GridViewSpreadExport.AddRow(Telerik.WinControls.UI.GridViewRowInfo gridViewRowInfo, int rowIndex) Line 960