IBM watson Discovery + Conversation - ibm-watson

Question

I followed the demo shown here. Everything works fine in the demo. But when I tried to use my discovery collection, it gave the error “Service seems to be down. Please try again after sometime or Please check the logs” and the local (wlp) server stopped. See the console log below. Where is the problem?
I used the workspace as used in the demo and changed the “Out-of-scope” intent questions. It retrieves answers from the conversation but not from the discovery?
[AUDIT ] CWWKZ0058I: Monitoring dropins for applications.
[AUDIT ] CWWKT0016I: Web application available (default_host): http://localhost:9080/
[AUDIT ] CWWKZ0001I: Application conversation-with-discovery-0.1-SNAPSHOT started in 10.257 seconds.
[AUDIT ] CWWKF0012I: The server installed the following features: [webProfile-7.0, jaxrs-2.0, json-1.0, appSecurity-2.0, jpa-2.1, cdi-1.2, jaxrsClient-2.0, distributedMap-1.0, websocket-1.1, el-3.0, beanValidation-1.1, ssl-1.0, jdbc-4.1, managedBeans-1.0, servlet-3.1, jsf-2.2, jsp-2.3, jndi-1.0, jsonp-1.0, ejbLite-3.2].
[AUDIT ] CWWKF0011I: The server defaultServer is ready to run a smarter planet.
2017-05-18 14:18:24,684 INFO Log4j appears to be running in a Servlet environment, but there's no log4j-web module available. If you want better web container support, please add the log4j-web JAR to your web archive or server lib directory.
14:18:24.817 [Default Executor-thread-13] INFO com.ibm.watson.apis.conversation_with_discovery.listener.AppServletContextListener - Deploying ServletContextListener
14:18:29.825 [Thread-12] INFO com.ibm.watson.apis.conversation_with_discovery.listener.SetupThread - Setup Complete
14:19:07.748 [Default Executor-thread-1] INFO com.ibm.watson.apis.conversation_with_discovery.discovery.DiscoveryClient - Creating Discovery Payload
[WARNING ] Application {http://rest.conversation_with_discovery.apis.watson.ibm.com/}ProxyResource has thrown exception, unwinding now
org.apache.cxf.interceptor.Fault
[WARNING ] Exception in handleFault on interceptor org.apache.cxf.jaxrs.interceptor.JAXRSDefaultFaultOutInterceptor#54b2f9b0
org.apache.cxf.interceptor.Fault
[ERROR ] Error occurred during error handling, give up!
org.apache.cxf.interceptor.Fault
[ERROR ] SRVE0777E: 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.postMessage(ProxyResource.java:192)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.ibm.ws.jaxrs20.server.LibertyJaxRsServerFactoryBean.performInvocation(LibertyJaxRsServerFactoryBean.java:674)
at [internal classes]