title: Spring AMQP - what if I return null in a Rabbit listener method with @SendTo annotation?
body: <p>Spring AMQP doc says:</p>
  
  <blockquote>
    <p>Assuming our processOrder method should now return an OrderStatus, it
    is possible to write it as follow to automatically send a reply:</p>
  </blockquote>
  
  <pre><code>@RabbitListener(destination = "myQueue")
  @SendTo("status")
  public OrderStatus processOrder(Order order) {
      // order processing
      return status;
  }
  </code></pre>
  
  <p>What if I return a null at the end of the processOrder method? Will it send a null object to MQ or simply do nothing?</p>