Exporting a WebList as a .csv

Hi, I am new in Xojo and I sincerly don´t know why, when exporting a WebListBox as a folderitem in Xojo2017 (with MBS plugins) I get an error saying: “Attempted to access cell -1,-1 but limit is 14,8.”

Here is the code I´m using:

Function exportCSV(extends lb As WebListbox) As folderitem

Dim excelOut As TextOutputStream

Dim f as FolderItem

f= SpecialFolder.Documents.child("test.csv")

excelOut = TextOutputStream.Create(f)

if excelOut <> nil then
  excelOut.Write lb.cell(-1,-1)
end if

return f

End Function

already been solved at OutOfBoundsException on WebListBox2017