Commented Unassigned: Array Formulas Messed Up On 4.0 Beta [14992]

Hello,

I have a workbook with a summary worksheet with array formulas and a data worksheet for inputting data with EPPlus. This worked very well with 3.1.3 but trying it with the new 4.0 Beta my array formulas are getting replaced with formulas such as "=1073741825". It appears that just saving the package causes the issue. Below is the code I used to test this. Attached is a test workbook.

```
using (ExcelPackage pck = new ExcelPackage(new System.IO.FileInfo("test.xlsx")))
{
pck.Save();
}
```

Thanks,
Tyler Brinkley
Comments: Fixed in latest source code (Default Branch). FormulaID was a string instead of an int.