Do not send parameters with undefined to body #719

[youngkaneda]

This prevents a undefined body to be passed on URL parameters

    if (value === undefined) {
        return;
    }

[youngkaneda]

@janschoenherr could you review this?

[NarHakobyan]

is this project maintaining? I think need to create new maintainable library :/

[youngkaneda]

maybe not, would be nice if the project dev had not discontinued.