in assets/js/slick.js [732:752]
    Slick.prototype.checkNavigable = function(index) {
        var _ = this,
            navigables, prevNavigable;
        navigables = _.getNavigableIndexes();
        prevNavigable = 0;
        if (index > navigables[navigables.length - 1]) {
            index = navigables[navigables.length - 1];
        } else {
            for (var n in navigables) {
                if (index < navigables[n]) {
                    index = prevNavigable;
                    break;
                }
                prevNavigable = navigables[n];
            }
        }
        return index;
    };