xml_func.py: XML functions that assume their last argument is a value (_map, etc.): Use new helper function pop_value() to retrieve this value. Return None if value is None because this indicates the input is empty.
xml_func.py: XML functions that assume their last argument is a value (_map, etc.): Use new helper function pop_value() to retrieve this value. Return None if value is None because this indicates the input is empty.