anchor.diff:      refresh_visible_rows(RowsToUpdate, NewFirstColShown, NofColsShown, RowDataList, ListAsStr),
   
          % Clear fields currently not visible.
  -    clear_fields(lists:nthtail(NofColsShown, NewColIds), 
  -		 lists:nthtail(NofRowsShown, NewRowIds)),
  +    clear_fields(safe_nthtail(NofColsShown, NewColIds),
  +		 safe_nthtail(NofRowsShown, NewRowIds)),
   
       
       NewGridP = GridP#grid_params{nof_cols        = NewNofCols,
  
positive.code: 
         % Update the ColWidths list.
      TempColWidths = lists:sublist(ColWidths, VirtualCol - 1) ++ 
  	[NewWidthOfCol | lists:nthtail(VirtualCol, ColWidths)],
      
         % Check the other columns, whether a new column has to be created.
      ColsShown    = compute_cols_shown(FirstColShown, TempColWidths, GridWidth, 
  
negative.code: 			ColWidthsLength < FirstColShown ->
  			    [];
  			true ->
  			    safe_nthtail(FirstColShown - 1, ColWidths)
  		    end,
      compute_cols_shown(UsedColWidths, GridWidth, DefaultColWidth).
  
  