Various window save/restore operations don't work if you have about:config on the here be dragons page

[ThosRTanner]

This function at the end of Session.js

TabGroupsManager.Session.prototype.tmpOverrideGetElementByIdForAboutConfig = function(tab)
{
  //http://zpao.com/posts/session-restore-changes-in-firefox-15/ > '#' removed > fx 15
  //Bug 947212 - Broadcast form data and move it out of tabData.entries[] > fx 29
  //let state = JSON.parse(this.sessionStore.getTabState(tab));
  //let textbox = state.formdata.id["textbox"];

  //no reason to fix this, there is always a textbox element for about:config - not sure when this will be called
  let ssData = tab.linkedBrowser.__SS_data;
  let textbox = ssData.entries[ssData.index - 1].formdata["#textbox"];
  tab.linkedBrowser.contentDocument.getElementById = function()
  {
    return {
      value: textbox
    }
  };
};

It lies