This is reported at https://gna.org/bugs/?22102.
The Sequence_2D GUI element used for all list of lists arguments in the user function GUI windows
now correctly handles variable length lists. The first column which shows a count of the elements
is now properly taken into account in the SetValue(), GetValue() and add_item() methods, via a new
self.offset variable. The self.variable_length variable has also been fixed so it is not
overwritten by the parent Sequence GUI element.
