NullPointerException in CXF producer endpoint used in Camel route.

Issue

We define a Camel route that consumes from a CXF endpoint, transforms the message and then sends the message to another external Web Service using a CXF producer endpoint. E.g.

<cxf:cxfEndpoint id="consumer" address="myRouteService/" serviceClass="...">
  <cxf:properties>
    <entry key="dataFormat" value="MESSAGE" />
  </cxf:properties>
</cxf:cxfEndpoint>

<cxf:cxfEndpoint id="producer" address="http://localhost:9000/myservice" serviceClass="...">
  <cxf:properties>
    <entry key="dataFormat" value="PAYLOAD" />
  </cxf:properties>
</cxf:cxfEndpoint>

<camelContext xmlns="http://camel.apache.org/schema/blueprint" trace="true">
  <route id="test" trace="true" streamCache="true">
      <from uri="cxf:bean:consumer"/>
      ...
      <camel:to uri="cxf:bean:producer"/>
</camelContext>

At runtime messages get routed successfully but we also see this NullPointerException in the log

java.lang.NullPointerException
  at org.apache.camel.component.cxf.DefaultCxfBinding.getResponsePayloadList(DefaultCxfBinding.java:434)[org.apache.camel:camel-cxf:2.15.1.redhat-621103]
  at org.apache.camel.component.cxf.DefaultCxfBinding.populateCxfResponseFromExchange(DefaultCxfBinding.java:350)[org.apache.camel:camel-cxf:2.15.1.redhat-621103]
  at org.apache.camel.component.cxf.CxfConsumer$1.setResponseBack(CxfConsumer.java:216)[org.apache.camel:camel-cxf:2.15.1.redhat-621103]
  at org.apache.camel.component.cxf.CxfConsumer$1.syncInvoke(CxfConsumer.java:143)[org.apache.camel:camel-cxf:2.15.1.redhat-621103]
  at org.apache.camel.component.cxf.CxfConsumer$1.invoke(CxfConsumer.java:78)[org.apache.camel:camel-cxf:2.15.1.redhat-621103]
  at org.apache.cxf.interceptor.ServiceInvokerInterceptor$1.run(ServiceInvokerInterceptor.java:59)[org.apache.cxf:cxf-core:3.0.4.redhat-621084]
  at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)[:1.8.0_66]
  at java.util.concurrent.FutureTask.run(FutureTask.java:266)[:1.8.0_66]
  at org.apache.cxf.interceptor.ServiceInvokerInterceptor$2.run(ServiceInvokerInterceptor.java:126)[org.apache.cxf:cxf-core:3.0.4.redhat-621084]
  at org.apache.cxf.workqueue.SynchronousExecutor.execute(SynchronousExecutor.java:37)[org.apache.cxf:cxf-core:3.0.4.redhat-621084]
  at org.apache.cxf.interceptor.ServiceInvokerInterceptor.handleMessage(ServiceInvokerInterceptor.java:131)[org.apache.cxf:cxf-core:3.0.4.redhat-621084]
  at org.apache.cxf.phase.PhaseInterceptorChain.doIntercept(PhaseInterceptorChain.java:307)[org.apache.cxf:cxf-core:3.0.4.redhat-621084]
  at org.apache.cxf.transport.ChainInitiationObserver.onMessage(ChainInitiationObserver.java:121)[org.apache.cxf:cxf-core:3.0.4.redhat-621084]
  at org.apache.cxf.transport.jms.JMSDestination.onMessage(JMSDestination.java:233)[org.apache.cxf:cxf-rt-transports-jms:3.0.4.redhat-621084]
  at org.apache.cxf.transport.jms.util.PollingMessageListenerContainer$XAPoller.run(PollingMessageListenerContainer.java:117)[org.apache.cxf:cxf-rt-transports-jms:3.0.4.redhat-621084]
  at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)[:1.8.0_66]
  at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)[:1.8.0_66]
  at java.lang.Thread.run(Thread.java:745)[:1.8.0_66]