Revert "set metadata default to no_value if default is None"

                 visible=True, set_in_upload=False, **kwargs):

        self.name = name

        self.desc = desc or name

        if default is None and no_value is not None:

            self.default = no_value

        else:

        self.default = default

        self.no_value = no_value

        self.visible = visible