Fix session history navigation: Fixes HTML5 session history navigation when the URL argument is specified but is `null` or `undefined`.

Fix session history navigation 1.01.js

// ==UserScript==
// @name Fix session history navigation
// @version 1.01
// @description Fixes HTML5 session history navigation when the URL argument is specified but is `null` or `undefined`.
// @author XP1 (https://github.com/XP1/)
// @namespace https://gist.github.com/1832301/
// @include http*://launchpad.net/*
// @include http*://*.launchpad.net/*
// ==/UserScript==

/*jslint browser: true, vars: true, white: true, maxerr: 50, indent: 4 */
(function (history)
{
    "use strict";

    function fixState(realStateFunction)
    {
        return function stateFunction(data, title, url)
        {
            return (typeof url === "string" ? realStateFunction.call(this, data, title, url) : realStateFunction.call(this, data, title));
        };
    }

    var realPushState = history.pushState;
    history.pushState = fixState(realPushState);

    var realReplaceState = history.replaceState;
    history.replaceState = fixState(realReplaceState);
}(this.history));

I posted this user JS in this thread:

launchpad.net bug search broken with Opera:
http://my.opera.com/community/forums/topic.dml?id=1303132