QTableWidget tables have scrolling problem when rows with multiple column span are present

The problem is that if a QTableWidget table contains a continuous block of rows that have multiple column spans, then the user may not be able to scroll down using the down arrow key if the current cell is located in a column that is not the first one.

To replicate this problem please first compile the source code that I attached. After opening up the executable press the down arrow key to scroll down the table. When the cursor reaches a row that has multiple column span then the table will stop scrolling down until the current cell finds a row that has single column span. This will cause the table to "magically" jump from a row one on end of the table to another row on a different end of the table. This problem happens when the user scrolls up too.

This problem is not new to Qt 4.6.2, since I detected it on Qt 4.6.0 as well.