TableView: cellAtPosition() doesn't provide valid cell information for all the cases

The TableView cellAtPosition() API doesn't provide valid cell information for the point outside the viewport.

How to reproduce:
1. Have more columns in the table view, such that the viewport covers only a part of it
2. Scroll to the last column and get the cell information for that point using cellAtPosition(point)

Actual:
Invalid cell information for the position outside the viewport

Expected:

Valid cell information for that position

Note to investigate:

The loadedColumns() have been used to compute the cell information for the point, which doesn't consider all the columns.