[flexcoders] DataGrid error when scrolling to last row and starting item edit

[technusiast]

Hi,

I have a subclass of the DataGrid, with two columns, each with its own 
renderer. One renderer has a button, which when clicked, starts item edit 
(consisting of a TextInput).

Consistently, when there are too many rows for one pageful, scrolling down to 
the last row and starting item edit, results in this error:

TypeError: Error #1010: A term is undefined and has no properties.
at 
mx.controls::DataGrid/commitEditedItemPosition()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\controls\DataGrid.as:4064]
at 
mx.controls::DataGrid/updateDisplayList()[E:\dev\4.0.0\frameworks\projects\framework\src\mx\controls\DataGrid.as:1804]
...

Any inputs on how to solve this greatly appreciated!

Line 4064 of the DataGrid class is:
var item:IListItemRenderer = 
actualContentHolder.listItems[actualRowIndex][actualColIndex];