wso2 esb 4.7 cannot handle JSON NULL object

when using esb4.7, after configure  like below:
 <clone continueParent="true">
         <target>
            <sequence>
               <send>
                  <endpoint key="rating_response_queue"/>
               </send>
            </sequence>
         </target>
      </clone>
      <send/>

and put it into out sequence
If there is NULL object in JSON, it will be changed to "NULL".
This is Log:

Original Response:

{"Appearances":[{"AppearanceType":"Age Range","AppearanceValue":"< 30"},{"AppearanceType":"Height","AppearanceValue":"Short"},{"AppearanceType":"Build","AppearanceValue":"Light"}],"Comments":"","Country":"null","Gender":"1","RefusalId":"201309040014","RefusalRatingSummary":"null","State":"null"}

After enable clone Response:
{"Appearances":[{"AppearanceType":"Age Range","AppearanceValue":"< 30"},{"AppearanceType":"Height","AppearanceValue":"Short"},{"AppearanceType":"Build","AppearanceValue":"Light"}],"Comments":"","Country":null,"Gender":1,"RefusalId":"201309040013","RefusalRatingSummary":null,"State":null}

This will crash our application