    # File lib/active_record/validations.rb, line 63
        def add_on_empty(attributes, msg = @@default_error_messages[:empty])
          for attr in [attributes].flatten
            value = @base.respond_to?(attr.to_s) ? @base.send(attr.to_s) : @base[attr.to_s]
            is_empty = value.respond_to?("empty?") ? value.empty? : false
            add(attr, msg) unless !value.nil? && !is_empty
          end
        end