Commented Unassigned: Unable to copy worksheets into other workbook [15350]

Hi,

We used EPPlus 3.1.3.3 till now and the following code worked very well.

```
private static ExcelPackage MergeExcelPackages(ExcelPackage aExcelPackage,
ExcelPackage bExcelPackage)
{
var excelPackage = new ExcelPackage();
excelPackage.Workbook.Worksheets.Add("AInfo", aExcelPackage.Workbook.Worksheets[1]);
excelPackage.Workbook.Worksheets.Add("BInfo", bExcelPackage.Workbook.Worksheets[1]);

return excelPackage;
}
```

Now, we are trying to upgrade EPPlus version to 4.0.4 and getting Index out of range error. Can you please let me know what's wrong with my code ?
Comments: Going back to the 4.0.0.0 Beta version fixed this issue for me.