v4.20 - не генерятся отчеты Excel

v4.16 - работает
v4.19 и v4.20 -
код:
ExcelStrategyReport report = new ExcelStrategyReport(_strategy, "sma.xls");
report.Generate();

выдает исключение:
NullReferenceException - "Ссылка на объект не указывает на экземпляр объекта."
StackTrace:
в Ecng.Interop.ExcelExporter.SetCell(Int32 col, Int32 row, Object value)
в StockSharp.Algo.Reporting.ExcelStrategyReport.Generate()
в SampleHistoryTesting.MainWindow.Report_Click(Object sender, RoutedEventArgs e) в D:\svalka\invest\_info\_sSharp\lib\StockSharp_4.0.20\Samples\Testing\SampleHistoryTesting\MainWindow.xaml.cs:строка 213
в System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
в System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
в System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
в System.Windows.UIElement.RaiseEvent(RoutedEventArgs e)
в System.Windows.Controls.Primitives.ButtonBase.OnClick()
в System.Windows.Controls.Button.OnClick()
в System.Windows.Controls.Primitives.ButtonBase.OnMouseLeftButtonUp(MouseButtonEventArgs e)
в System.Windows.UIElement.OnMouseLeftButtonUpThunk(Object sender, MouseButtonEventArgs e)
в System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
в System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
в System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
в System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
в System.Windows.UIElement.ReRaiseEventAs(DependencyObject sender, RoutedEventArgs args, RoutedEvent newEvent)
в System.Windows.UIElement.OnMouseUpThunk(Object sender, MouseButtonEventArgs e)
в System.Windows.Input.MouseButtonEventArgs.InvokeEventHandler(Delegate genericHandler, Object genericTarget)
в System.Windows.RoutedEventArgs.InvokeHandler(Delegate handler, Object target)
в System.Windows.RoutedEventHandlerInfo.InvokeHandler(Object target, RoutedEventArgs routedEventArgs)
в System.Windows.EventRoute.InvokeHandlersImpl(Object source, RoutedEventArgs args, Boolean reRaised)
в System.Windows.UIElement.RaiseEventImpl(DependencyObject sender, RoutedEventArgs args)
в System.Windows.UIElement.RaiseTrustedEvent(RoutedEventArgs args)
в System.Windows.UIElement.RaiseEvent(RoutedEventArgs args, Boolean trusted)
в System.Windows.Input.InputManager.ProcessStagingArea()
в System.Windows.Input.InputManager.ProcessInput(InputEventArgs input)
в System.Windows.Input.InputProviderSite.ReportInput(InputReport inputReport)
в System.Windows.Interop.HwndMouseInputProvider.ReportInput(IntPtr hwnd, InputMode mode, Int32 timestamp, RawMouseActions actions, Int32 x, Int32 y, Int32 wheel)
в System.Windows.Interop.HwndMouseInputProvider.FilterMessage(IntPtr hwnd, WindowMessage msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
в System.Windows.Interop.HwndSource.InputFilterMessage(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
в MS.Win32.HwndWrapper.WndProc(IntPtr hwnd, Int32 msg, IntPtr wParam, IntPtr lParam, Boolean& handled)
в MS.Win32.HwndSubclass.DispatcherCallbackOperation(Object o)
в System.Windows.Threading.ExceptionWrapper.InternalRealCall(Delegate callback, Object args, Int32 numArgs)
в MS.Internal.Threading.ExceptionFilterHelper.TryCatchWhen(Object source, Delegate method, Object args, Int32 numArgs, Delegate catchHandler)

похоже на багу. если написал в неправильную ветку - извините.