Bug found in refresh content in Grid.

According to the message post "Refresh content in grid", I used the solution provided for refresh content in Grid by Alex and NK:

obj.clearScrollModel();
obj.clearSelectedModel();
obj.clearSortModel();
obj.clearRowModel();
obj.setRowCount(...);
obj.refresh();

If I have many rows which has to be a vertical scroll bar, tried to select multiple rows with holding "CTRL" key and do some action, such as remove multiple rows. Then try to refresh the table. I got the javascript error with:

Error: mydata[...] is null or not an object.

Do anyone has any idea why it happens?

Thanks