Hi

First of all, thank you for this great module!

The file it concerns:
md_slider/js/md-slider-field-configure.js
Version: 7.x-2.17

Problem:
You check the wrong value.

//// Original ////
Lines 21-23:

var sliderId = $(this).val(),
sliderId = $(".fake-select-slider").find("option[value=" + sliderId + "]").data('sliderid');
if (sliderId != -1) { ...

//// END Original ////

//// Bugfix-Example ////
Lines 21-23:

var sliderId = $(this).val();
if (sliderId != -1) {
var sliderId = $(".fake-select-slider").find("option[value=" + sliderId + "]").data('sliderid');

//// END Bugfix-Example ////

You also can check for "undefined":

if ( typeof obj !== "undefined" ) ... You choose! :)

Thanks you.
Regards,
The Globonet-Team