Created Unassigned: HSSFShapeGroup constructor doesn't work [13460]

Hello,

I am using NPOI last beta version to handle a xlsx file with several dates.
If I want to create a new instance of HSSFShapeGroup class, like this:

SSFClientAnchor anchor = new HSSFClientAnchor(0, 0, 1023, 255, 2,25, 19, 27);
HSSFShapeGroup shapeGroup = new HSSFShapeGroup(null, anchor);

I get the following result for shapeGroup properties:

FillColor: '(((NPOI.HSSF.UserModel.HSSFShape)(shapeGroup))).FillColor' threw an exception of type 'System.NullReferenceException'
IsFlipHorizontal: '(((NPOI.HSSF.UserModel.HSSFShape)(shapeGroup))).IsFlipHorizontal' threw an exception of type 'System.NullReferenceException'
IsFlipVertical: '(((NPOI.HSSF.UserModel.HSSFShape)(shapeGroup))).IsFlipVertical' threw an exception of type 'System.NullReferenceException'
IsNoFill: '(((NPOI.HSSF.UserModel.HSSFShape)(shapeGroup))).IsNoFill' threw an exception of type 'System.NullReferenceException'
LineStyle: '(((NPOI.HSSF.UserModel.HSSFShape)(shapeGroup))).LineStyle' threw an exception of type 'System.NullReferenceException'
LineStyleColor: '(((NPOI.HSSF.UserModel.HSSFShape)(shapeGroup))).LineStyleColor' threw an exception of type 'System.NullReferenceException'
LineWidth: '(((NPOI.HSSF.UserModel.HSSFShape)(shapeGroup))).LineWidth' threw an exception of type 'System.NullReferenceException'
RotationDegree: '(((NPOI.HSSF.UserModel.HSSFShape)(shapeGroup))).RotationDegree' threw an exception of type 'System.NullReferenceException'

There is a possibility to create a new instance of HSSFShapeGroup class that works properly?
Thanks !