I want to display chart with Chinese, so I change library setting in the run time.

org.zkoss.lang.Library.setProperty("org.zkoss.zss.chart.title.font", "SansSerif, Italic, 30");
org.zkoss.lang.Library.setProperty("org.zkoss.zss.chart.legend.font", "SansSerif, plain, 18");
org.zkoss.lang.Library.setProperty("org.zkoss.zss.chart.xAxisTick.font", "SansSerif, bold, 16");
org.zkoss.lang.Library.setProperty("org.zkoss.zss.chart.xAxis.font", "SansSerif, bold, 18");

After I set above property, if there exist a chart without title throws NPE:

嚴重的: >>java.lang.NullPointerException
>> at org.zkoss.zkex.zul.impl.JFreeChartEngine.drawChart(JFreeChartEngine.java:364)
>> at org.zkoss.zul.Chart.doSmartDraw(Chart.java:243)
>> at org.zkoss.zul.Chart.access$100(Chart.java:82)
>> at org.zkoss.zul.Chart$SmartDrawListener.onEvent(Chart.java:224)
>> at org.zkoss.zk.ui.AbstractComponent.onEvent(AbstractComponent.java:2743)
>> at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2714)
>> at org.zkoss.zk.ui.AbstractComponent.service(AbstractComponent.java:2655)
>> at org.zkoss.zk.ui.impl.EventProcessor.process(EventProcessor.java:136)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.processEvent(UiEngineImpl.java:1720)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.process(UiEngineImpl.java:1505)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage0(UiEngineImpl.java:467)
>> at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage(UiEngineImpl.java:312)
>> at org.zkoss.zk.ui.http.DHtmlLayoutServlet.process(DHtmlLayoutServlet.java:215)
>> at org.zkoss.zk.ui.http.DHtmlLayoutServlet.doGet(DHtmlLayoutServlet.java:136)
>> at javax.servlet.http.HttpServlet.service(HttpServlet.java:707)
>> at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
>> at org.mortbay.jetty.servlet.ServletHolder.handle(ServletHolder.java:511)
>> at org.mortbay.jetty.servlet.ServletHandler.handle(ServletHandler.java:401)
>> at org.mortbay.jetty.security.SecurityHandler.handle(SecurityHandler.java:216)
>> at org.mortbay.jetty.servlet.SessionHandler.handle(SessionHandler.java:182)
>> at org.mortbay.jetty.handler.ContextHandler.handle(ContextHandler.java:766)
>> at org.mortbay.jetty.webapp.WebAppContext.handle(WebAppContext.java:450)
>> at org.mortbay.jetty.handler.HandlerWrapper.handle(HandlerWrapper.java:152)
>> at org.mortbay.jetty.Server.handle(Server.java:326)
>> at org.mortbay.jetty.HttpConnection.handleRequest(HttpConnection.java:542)
>> at org.mortbay.jetty.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:928)
>> at org.mortbay.jetty.HttpParser.parseNext(HttpParser.java:549)
>> at org.mortbay.jetty.HttpParser.parseAvailable(HttpParser.java:212)
>> at org.mortbay.jetty.HttpConnection.handle(HttpConnection.java:404)
>> at org.mortbay.io.nio.SelectChannelEndPoint.run(SelectChannelEndPoint.java:410)
>> at org.mortbay.thread.QueuedThreadPool$PoolThread.run(QueuedThreadPool.java:582)

You can use chart-issue.xlsx to reproduce this issue, by using the library setting code above.