title: Error while calling Discovery service in conversation-with-discoveryapplication
body: <p>I have used <a href="https://github.com/watson-developer-cloud/conversation-with-discovery" rel="nofollow noreferrer">https://github.com/watson-developer-cloud/conversation-with-discovery</a> code and deployed application in Bluemix, when I am testing the application conversation is working but discovery service is not working .</p>
  
  <p>I have added OUT_OF_Scope intent with call_discovery action.</p>
  
  <p>I am getting server is busy error when we give out scope question in chatbot.</p>
  
  <p>below is the  the log error , please help me to resolve this error.
  Exception thrown by application class 'com.ibm.watson.apis.conversation_with_discovery.rest.ProxyResource.postMessage:192'
  java.lang.NullPointerException
      at com.ibm.watson.apis.conversation_with_discovery.rest.ProxyResource.pos</p>