NPE in Undertow

Error message
java.lang.NullPointerException: java.lang.NullPointerException

Stack trace
…ndertow.server.protocol.http.HttpResponseConduit.write (HttpResponseConduit.java:638)

      org.xnio.conduits.AbstractStreamSinkConduit.write (AbstractStreamSinkConduit.java:55)

…uits.DeflatingStreamSinkConduit.performFlushIfRequired (DeflatingStreamSinkConduit.java:399)

  io.undertow.conduits.DeflatingStreamSinkConduit.flush (DeflatingStreamSinkConduit.java:344)

       org.xnio.conduits.ConduitStreamSinkChannel.flush (ConduitStreamSinkChannel.java:162)

 io.undertow.channels.DetachableStreamSinkChannel.flush (DetachableStreamSinkChannel.java:119)

               org.xnio.channels.Channels.flushBlocking (Channels.java:63)

              io.undertow.io.UndertowOutputStream.close (UndertowOutputStream.java:344)

                io.undertow.io.BlockingSenderImpl.close (BlockingSenderImpl.java:174)

            io.undertow.io.DefaultIoCallback.onComplete (DefaultIoCallback.java:54)

     io.undertow.io.BlockingSenderImpl.invokeOnComplete (BlockingSenderImpl.java:230)

                 io.undertow.io.BlockingSenderImpl.send (BlockingSenderImpl.java:99)

                 io.undertow.io.BlockingSenderImpl.send (BlockingSenderImpl.java:121)

…server.undertow.HttpServerExchangeData.setResponseBody (HttpServerExchangeData.java:92)

…ocktix.server.undertow.RestMethodHandler.handleRequest (RestMethodHandler.java:86)

…ocktix.server.undertow.RestMethodHandler.handleRequest (RestMethodHandler.java:66)

…ers.undertow.http.RequiresAnyRoleHandler.handleRequest (RequiresAnyRoleHandler.java:54)

…urity.handlers.AuthenticationCallHandler.handleRequest (AuthenticationCallHandler.java:52)

…handlers.AuthenticationConstraintHandler.handleRequest (AuthenticationConstraintHandler.java:51)

…dertow.server.handlers.AttachmentHandler.handleRequest (AttachmentHandler.java:50)

        io.undertow.server.RoutingHandler.handleRequest (RoutingHandler.java:93)

…server.handlers.encoding.EncodingHandler.handleRequest (EncodingHandler.java:72)

…handlers.AuthenticationMechanismsHandler.handleRequest (AuthenticationMechanismsHandler.java:60)

…bstractSecurityContextAssociationHandler.handleRequest (AbstractSecurityContextAssociationHandler.java:43)

…ers.undertow.http.SecurityContextHandler.handleRequest (SecurityContextHandler.java:38)

…andlers.undertow.http.PersistenceHandler.handleRequest (PersistenceHandler.java:35)

…ix.handlers.undertow.http.SessionHandler.handleRequest (SessionHandler.java:31)

….server.session.SessionAttachmentHandler.handleRequest (SessionAttachmentHandler.java:68)

…andlers.undertow.http.TockVersionHandler.handleRequest (TockVersionHandler.java:41)

…ndlers.undertow.http.GenericErrorHandler.handleRequest (GenericErrorHandler.java:32)

…andlers.undertow.http.ExchangeLogHandler.handleRequest (ExchangeLogHandler.java:58)

…ertow.http.RequestScopeHandler.lambda$handleRequest$68 (RequestScopeHandler.java:19)

   com.google.inject.servlet.ServletScopes$Context.call (ServletScopes.java:375)

         com.google.inject.servlet.ServletScopes$7.call (ServletScopes.java:344)

…ndlers.undertow.http.RequestScopeHandler.handleRequest (RequestScopeHandler.java:21)

       io.undertow.server.Connectors.executeRootHandler (Connectors.java:202)

            io.undertow.server.HttpServerExchange$1.run (HttpServerExchange.java:793)

      java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1142)

     java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:617)

                                   java.lang.Thread.run (Thread.java:745)