Restrict the null body from entering into a camel endpoint in xml

<camel:route id="messageRoute">    
<camel:from ref="fromMessageQueue" />
<camel:processor ref="queueMessageProcessor" />
<camel:to ref="toMessageQueue" />
</camel:route>

In this code snippet, receiving a message from q queue then processing it in queue message processor, finally placing it into to message queue. While processing the message in processor, the body of exchange is getting set to null. I need to prevent the exchange with null body from entering into to message queue.