java.lang.NullPointerException: null
	at org.vaadin.addons.ComboBoxMultiselect.lambda$internalSetDataProvider$c8a42f1e$1(ComboBoxMultiselect.java:719) ~[vaadin-combobox-multiselect-2.4.jar!/:2.4]
	at java.util.TimSort.countRunAndMakeAscending(Unknown Source) ~[?:1.8.0_74]
	at java.util.TimSort.sort(Unknown Source) ~[?:1.8.0_74]
	at java.util.Arrays.sort(Unknown Source) ~[?:1.8.0_74]
	at java.util.stream.SortedOps$SizedRefSortingSink.end(Unknown Source) ~[?:1.8.0_74]
	at java.util.stream.AbstractPipeline.copyIntoWithCancel(Unknown Source) ~[?:1.8.0_74]
	at java.util.stream.AbstractPipeline.copyInto(Unknown Source) ~[?:1.8.0_74]
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(Unknown Source) ~[?:1.8.0_74]
	at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(Unknown Source) ~[?:1.8.0_74]
	at java.util.stream.AbstractPipeline.evaluate(Unknown Source) ~[?:1.8.0_74]
	at java.util.stream.ReferencePipeline.collect(Unknown Source) ~[?:1.8.0_74]
	at com.vaadin.data.provider.DataCommunicator.fetchItemsWithRange(DataCommunicator.java:374) ~[vaadin-server-8.3.1.jar!/:8.3.1]
	at com.vaadin.data.provider.DataCommunicator.sendDataToClient(DataCommunicator.java:336) ~[vaadin-server-8.3.1.jar!/:8.3.1]
	at com.vaadin.data.provider.DataCommunicator.beforeClientResponse(DataCommunicator.java:311) ~[vaadin-server-8.3.1.jar!/:8.3.1]
	at com.vaadin.server.communication.UidlWriter.write(UidlWriter.java:126) ~[vaadin-server-8.3.1.jar!/:8.3.1]
	at com.vaadin.server.communication.AtmospherePushConnection.push(AtmospherePushConnection.java:168) ~[vaadin-server-8.3.1.jar!/:8.3.1]
	at com.vaadin.server.communication.PushHandler.lambda$new$1(PushHandler.java:146) ~[vaadin-server-8.3.1.jar!/:8.3.1]
	at com.vaadin.server.communication.PushHandler.callWithUi(PushHandler.java:235) [vaadin-server-8.3.1.jar!/:8.3.1]
	at com.vaadin.server.communication.PushHandler.onMessage(PushHandler.java:520) [vaadin-server-8.3.1.jar!/:8.3.1]
	at com.vaadin.server.communication.PushAtmosphereHandler.onMessage(PushAtmosphereHandler.java:87) [vaadin-server-8.3.1.jar!/:8.3.1]
	at com.vaadin.server.communication.PushAtmosphereHandler.onRequest(PushAtmosphereHandler.java:77) [vaadin-server-8.3.1.jar!/:8.3.1]
	at org.atmosphere.cpr.AsynchronousProcessor.action(AsynchronousProcessor.java:223) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.atmosphere.cpr.AsynchronousProcessor.suspended(AsynchronousProcessor.java:115) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.atmosphere.container.Servlet30CometSupport.service(Servlet30CometSupport.java:67) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.atmosphere.cpr.AtmosphereFramework.doCometSupport(AtmosphereFramework.java:2284) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.atmosphere.websocket.DefaultWebSocketProcessor.dispatch(DefaultWebSocketProcessor.java:593) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.atmosphere.websocket.DefaultWebSocketProcessor$3.run(DefaultWebSocketProcessor.java:345) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.atmosphere.util.VoidExecutorService.execute(VoidExecutorService.java:101) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.atmosphere.websocket.DefaultWebSocketProcessor.dispatch(DefaultWebSocketProcessor.java:340) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.atmosphere.websocket.DefaultWebSocketProcessor.invokeWebSocketProtocol(DefaultWebSocketProcessor.java:447) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.atmosphere.container.JSR356Endpoint$3.onMessage(JSR356Endpoint.java:272) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.atmosphere.container.JSR356Endpoint$3.onMessage(JSR356Endpoint.java:269) [atmosphere-runtime-2.4.11.vaadin2.jar!/:2.4.11.vaadin2]
	at org.apache.tomcat.websocket.WsFrameBase.sendMessageText(WsFrameBase.java:395) [tomcat-embed-websocket-8.5.28.jar!/:8.5.28]
	at org.apache.tomcat.websocket.server.WsFrameServer.sendMessageText(WsFrameServer.java:119) [tomcat-embed-websocket-8.5.28.jar!/:8.5.28]
	at org.apache.tomcat.websocket.WsFrameBase.processDataText(WsFrameBase.java:495) [tomcat-embed-websocket-8.5.28.jar!/:8.5.28]
	at org.apache.tomcat.websocket.WsFrameBase.processData(WsFrameBase.java:294) [tomcat-embed-websocket-8.5.28.jar!/:8.5.28]
	at org.apache.tomcat.websocket.WsFrameBase.processInputBuffer(WsFrameBase.java:133) [tomcat-embed-websocket-8.5.28.jar!/:8.5.28]
	at org.apache.tomcat.websocket.server.WsFrameServer.onDataAvailable(WsFrameServer.java:82) [tomcat-embed-websocket-8.5.28.jar!/:8.5.28]
	at org.apache.tomcat.websocket.server.WsFrameServer.doOnDataAvailable(WsFrameServer.java:171) [tomcat-embed-websocket-8.5.28.jar!/:8.5.28]
	at org.apache.tomcat.websocket.server.WsFrameServer.notifyDataAvailable(WsFrameServer.java:151) [tomcat-embed-websocket-8.5.28.jar!/:8.5.28]
	at org.apache.tomcat.websocket.server.WsHttpUpgradeHandler.upgradeDispatch(WsHttpUpgradeHandler.java:148) [tomcat-embed-websocket-8.5.28.jar!/:8.5.28]
	at org.apache.coyote.http11.upgrade.UpgradeProcessorInternal.dispatch(UpgradeProcessorInternal.java:54) [tomcat-embed-core-8.5.28.jar!/:8.5.28]
	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:53) [tomcat-embed-core-8.5.28.jar!/:8.5.28]
	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790) [tomcat-embed-core-8.5.28.jar!/:8.5.28]
	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1459) [tomcat-embed-core-8.5.28.jar!/:8.5.28]
	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) [tomcat-embed-core-8.5.28.jar!/:8.5.28]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) [?:1.8.0_74]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) [?:1.8.0_74]
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) [tomcat-embed-core-8.5.28.jar!/:8.5.28]
	at java.lang.Thread.run(Unknown Source) [?:1.8.0_74]