handle case with no properties for scope

Author: krasnoukhov

lib/rspec_api_documentation/writers/open_api_writer.rb

@@ -268,6 +268,8 @@ def inject_body_parameter(schema, parameter)
           scope = scope.properties[curr.to_s]
         end
 
+        return unless scope.properties
+
         scope.required ||= []
         scope.required << parameter[:name].to_s if parameter[:required]