def clear
      return if commontable.blank? || !is_closed?
      new_thread = Thread.new
      new_thread.commontable = commontable

      with_lock do
        self.commontable = nil
        save!
        new_thread.save!
        subscriptions.each do |s|
          s.thread = new_thread
          s.save!
        end
      end
    end
def clear
      return if commontable.blank? || !is_closed?
      new_thread = Thread.new
      new_thread.commontable = commontable

      with_lock do
        self.commontable = nil
        save!
        new_thread.save!
        subscriptions.each do |s|
          s.thread = new_thread
          s.save!
        end
      end
    end
Creates a new empty thread and assigns it to the commontable
 The old thread is kept in the database for archival purposes