SEVERE: 
java.lang.IllegalArgumentException: Response cannot be null
	at javax.servlet.ServletResponseWrapper.<init>(ServletResponseWrapper.java:89)
	at javax.servlet.http.HttpServletResponseWrapper.<init>(HttpServletResponseWrapper.java:85)
	at org.zkoss.web.servlet.http.HttpBufferedResponse.<init>(HttpBufferedResponse.java:71)
	at org.zkoss.web.servlet.http.HttpBufferedResponse.getInstance(HttpBufferedResponse.java:54)
	at org.zkoss.zk.ui.http.ExecutionImpl.dispatch(ExecutionImpl.java:242)
	at org.zkoss.zk.ui.http.ExecutionImpl.include(ExecutionImpl.java:203)
	at org.zkoss.zul.Include.include(Include.java:706)
	at org.zkoss.zul.Include.renderProperties(Include.java:628)
	at org.zkoss.zk.ui.AbstractComponent.redraw(AbstractComponent.java:2153)
	at org.zkoss.zk.ui.impl.UiVisualizer.redraw(UiVisualizer.java:1003)
	at org.zkoss.zk.ui.impl.UiVisualizer.getResponses(UiVisualizer.java:699)
	at org.zkoss.zk.ui.impl.UiEngineImpl.getResponses(UiEngineImpl.java:1531)
	at org.zkoss.zk.ui.impl.UiEngineImpl.execUpdate(UiEngineImpl.java:1337)
	at org.zkoss.zkmax.au.websocket.WebSocketEndPoint.process(WebSocketEndPoint.java:238)
	at org.zkoss.zkmax.au.websocket.WebSocketEndPoint.access$000(WebSocketEndPoint.java:58)
	at org.zkoss.zkmax.au.websocket.WebSocketEndPoint$1.onMessage(WebSocketEndPoint.java:101)
	at org.zkoss.zkmax.au.websocket.WebSocketEndPoint$1.onMessage(WebSocketEndPoint.java:98)
	at org.eclipse.jetty.websocket.jsr356.messages.TextWholeMessage.messageComplete(TextWholeMessage.java:56)
	at org.eclipse.jetty.websocket.jsr356.endpoints.JsrEndpointEventDriver.onTextFrame(JsrEndpointEventDriver.java:218)
	at org.eclipse.jetty.websocket.common.events.AbstractEventDriver.incomingFrame(AbstractEventDriver.java:162)
	at org.eclipse.jetty.websocket.common.WebSocketSession.incomingFrame(WebSocketSession.java:375)
	at org.eclipse.jetty.websocket.common.extensions.AbstractExtension.nextIncomingFrame(AbstractExtension.java:182)
	at org.eclipse.jetty.websocket.common.extensions.compress.PerMessageDeflateExtension.nextIncomingFrame(PerMessageDeflateExtension.java:105)
	at org.eclipse.jetty.websocket.common.extensions.compress.CompressExtension.forwardIncoming(CompressExtension.java:142)
	at org.eclipse.jetty.websocket.common.extensions.compress.PerMessageDeflateExtension.incomingFrame(PerMessageDeflateExtension.java:85)
	at org.eclipse.jetty.websocket.common.extensions.ExtensionStack.incomingFrame(ExtensionStack.java:220)
	at org.eclipse.jetty.websocket.common.Parser.notifyFrame(Parser.java:220)
	at org.eclipse.jetty.websocket.common.Parser.parse(Parser.java:256)
	at org.eclipse.jetty.websocket.common.io.AbstractWebSocketConnection.readParse(AbstractWebSocketConnection.java:679)
	at org.eclipse.jetty.websocket.common.io.AbstractWebSocketConnection.onFillable(AbstractWebSocketConnection.java:511)
	at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:279)
	at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:110)
	at org.eclipse.jetty.io.ChannelEndPoint$2.run(ChannelEndPoint.java:124)
	at org.eclipse.jetty.util.thread.Invocable.invokePreferred(Invocable.java:128)
	at org.eclipse.jetty.util.thread.Invocable$InvocableExecutor.invoke(Invocable.java:222)
	at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.doProduce(EatWhatYouKill.java:294)
	at org.eclipse.jetty.util.thread.strategy.EatWhatYouKill.run(EatWhatYouKill.java:199)
	at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:673)
	at org.eclipse.jetty.util.thread.QueuedThreadPool$2.run(QueuedThreadPool.java:591)
	at java.lang.Thread.run(Thread.java:748)