現タブが about:blank や about:newtab だったら、:tabopen でも現タブに開くモンキーパッチ

tabopen.js

commands.get("tabopen").action = function (args) {
  let special = args.bang;
  args = args.string;
  if (options.get("activate").has("all", "tabopen"))
    special = !special;

  let where = special ? liberator.NEW_TAB : liberator.NEW_BACKGROUND_TAB;

  if (buffer.URL === "about:blank" ||
  buffer.URL === "about:newtab")
    where = liberator.CURRENT_TAB;

  if (args)
    liberator.open(args, { where: where });
  else
    liberator.open("", { where: where });
};