in assets/js/slick.js [2945:2978]
    Slick.prototype.updateArrows = function() {
        var _ = this,
            centerOffset;
        centerOffset = Math.floor(_.options.slidesToShow / 2);
        if ( _.options.arrows === true &&
            _.slideCount > _.options.slidesToShow &&
            !_.options.infinite ) {
            _.$prevArrow.removeClass('slick-disabled').attr('aria-disabled', 'false');
            _.$nextArrow.removeClass('slick-disabled').attr('aria-disabled', 'false');
            if (_.currentSlide === 0) {
                _.$prevArrow.addClass('slick-disabled').attr('aria-disabled', 'true');
                _.$nextArrow.removeClass('slick-disabled').attr('aria-disabled', 'false');
            } else if (_.currentSlide >= _.slideCount - _.options.slidesToShow && _.options.centerMode === false) {
                _.$nextArrow.addClass('slick-disabled').attr('aria-disabled', 'true');
                _.$prevArrow.removeClass('slick-disabled').attr('aria-disabled', 'false');
            } else if (_.currentSlide >= _.slideCount - 1 && _.options.centerMode === true) {
                _.$nextArrow.addClass('slick-disabled').attr('aria-disabled', 'true');
                _.$prevArrow.removeClass('slick-disabled').attr('aria-disabled', 'false');
            }
        }
    };