Fix fatal error when printing :sing_static warning.

      @relations.each do |cls|

        if cls[:singleton]

          cls.find_members({:local => true, :static => true}).each do |m|

            warn(:sing_static, "Static members don't make sense in singleton class #{@doc[:name]}", m)

            warn(:sing_static, "Static members don't make sense in singleton class #{cls[:name]}", m)

          end

        end

      end