Fix crash when method inherits from cfg.

        each_member do |member|

          if member[:tagname] == :method

            optional_found = false

            member[:params].each do |p|

            Array(member[:params]).each do |p|

              if optional_found && !p[:optional]

                warn(:req_after_opt, "Optional param followed by regular param #{p[:name]}", member)

              end