If a excel File has no WorkbookProperties defined the document load fails.
ClosedXML.Excel.XLWorkbook_Load.cs
var date1904 = dSpreadsheet.WorkbookPart.Workbook.WorkbookProperties.Date1904;
It raise "Object reference not set to an instance of an object"
ClosedXML.Excel.XLWorkbook_Load.cs
var date1904 = dSpreadsheet.WorkbookPart.Workbook.WorkbookProperties.Date1904;
It raise "Object reference not set to an instance of an object"