ERROR {org.apache.synapse.core.axis2.Axis2Sender} -  Unexpected error during sending message out {org.apache.synapse.core.axis2.Axis2Sender}
java.lang.NullPointerException
                at org.apache.synapse.transport.passthru.PassThroughHttpSender.invoke(PassThroughHttpSender.java:270)
                at org.apache.axis2.engine.AxisEngine.send(AxisEngine.java:442)
                at org.apache.synapse.core.axis2.DynamicAxisOperation$DynamicOperationClient.send(DynamicAxisOperation.java:185)
                at org.apache.synapse.core.axis2.DynamicAxisOperation$DynamicOperationClient.executeImpl(DynamicAxisOperation.java:167)
                at org.apache.axis2.client.OperationClient.execute(OperationClient.java:149)
                at org.apache.synapse.core.axis2.Axis2FlexibleMEPClient.send(Axis2FlexibleMEPClient.java:605)
                at org.apache.synapse.core.axis2.Axis2Sender.sendOn(Axis2Sender.java:85)
                at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.send(Axis2SynapseEnvironment.java:547)
                at org.apache.synapse.endpoints.AbstractEndpoint.send(AbstractEndpoint.java:384)
                at org.apache.synapse.endpoints.HTTPEndpoint.send(HTTPEndpoint.java:85)
                at org.apache.synapse.endpoints.IndirectEndpoint.send(IndirectEndpoint.java:55)
                at org.apache.synapse.mediators.builtin.SendMediator.mediate(SendMediator.java:121)
                at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:108)
                at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:70)
                at org.apache.synapse.mediators.filters.FilterMediator.mediate(FilterMediator.java:169)
                at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:108)
                at org.apache.synapse.mediators.AbstractListMediator.mediate(AbstractListMediator.java:70)
                at org.apache.synapse.mediators.base.SequenceMediator.mediate(SequenceMediator.java:158)
                at org.apache.synapse.rest.Resource.process(Resource.java:351)
                at org.apache.synapse.rest.API.process(API.java:417)
                at org.apache.synapse.rest.RESTRequestHandler.dispatchToAPI(RESTRequestHandler.java:90)
                at org.apache.synapse.rest.RESTRequestHandler.process(RESTRequestHandler.java:69)
                at org.apache.synapse.core.axis2.Axis2SynapseEnvironment.injectMessage(Axis2SynapseEnvironment.java:303)
                at org.apache.synapse.core.axis2.SynapseMessageReceiver.receive(SynapseMessageReceiver.java:92)
                at org.apache.axis2.engine.AxisEngine.receive(AxisEngine.java:180)
                at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler_aroundBody0(ServerWorker.java:337)
                at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler_aroundBody1$advice(ServerWorker.java:80)
                at org.apache.synapse.transport.passthru.ServerWorker.processNonEntityEnclosingRESTHandler(ServerWorker.java:1)
                at org.apache.synapse.transport.passthru.ServerWorker.processEntityEnclosingRequest_aroundBody2(ServerWorker.java:383)
                at org.apache.synapse.transport.passthru.ServerWorker.processEntityEnclosingRequest_aroundBody3$advice(ServerWorker.java:50)
                at org.apache.synapse.transport.passthru.ServerWorker.processEntityEnclosingRequest(ServerWorker.java:1)
                at org.apache.synapse.transport.passthru.ServerWorker.run(ServerWorker.java:151)
                at org.apache.axis2.transport.base.threads.NativeWorkerPool$1.run(NativeWorkerPool.java:172)
                at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
                at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
                at java.lang.Thread.run(Thread.java:748)