code: @Override
     protected Object handleDefault(InvocationContext ctx, VisitableCommand command) throws Throwable {
        return invokeNextInterceptor(ctx, command);
     }
docs: The default behaviour of the visitXXX methods, which is to ignore the call and pass the call up to the next
  interceptor in the chain.
  
  @param ctx     invocation context
  @param command command to invoke
  @return return value
  @throws Throwable in the event of problems