lessThan reports error if compared to empty field about jquery-validation HOT 3 OPEN

j.validator.addMethod(
    "lessThanIfOtherNotEmpty",
    function (val1, element, param) {
        var target = j(param);

        // if (
        //     this.settings.onfocusout &&
        //     target.not(".validate-lessThanIfOtherNotEmpty-blur").length
        // ) {
        //     target
        //         .addClass("validate-lessThanIfOtherNotEmpty-blur")
        //         .on("blur.validate-lessThanIfOtherNotEmpty", function () {
        //             j(element).valid();
        //         });
        // }
        var val2 = target.val(),
            normalizer;
        if ((rules = target.rules())) {
            if (typeof rules.normalizer === "function") {
                normalizer = rules.normalizer;
            } else if (typeof this.settings.normalizer === "function") {
                normalizer = this.settings.normalizer;
            }
            // If normalizer is defined, then call it to retreive the changed value instead
            // of using the real one.
            // Note that `this` in the normalizer is `element`.
            if (normalizer) {
                val2 = normalizer.call(element, val2);

                // Delete the normalizer from rules to avoid treating it as a pre-defined method.
                delete rules.normalizer;
            }
        }

        if (val1 == "" || val2 == "") {
            return true;
        }

        return val1 < val2;
    },
    "Please enter a lesser value."
);