Returns populated row at given index.
If Row 1 and Row 3 have data in them but Row 2 has no data or formatting then the number of populated rows is 2.
In the case where Row 1 and Row 3 have data and Row 2 has no data then Row 1 will have index of 0 and row 3 will have index of 1. While Row 2 is not included in the list of populated rows.