docs: function addonsManager_getCategoryById(aSpec) {
      var spec = aSpec || { };
      var id = spec.id;
  
      if (!id)
        throw new Error(arguments.callee.name + ": Category ID not specified.");
  
      return this.getCategories({
        attribute: "id",
        value: "category-" + id
      })[0];
    }