Reproducing Steps

Load attached excel file to Spreadsheet, and you can see:

java.lang.NullPointerException
at org.zkoss.zss.ui.impl.Utils.escapeCellText(Utils.java:628)
at org.zkoss.zss.ui.impl.Utils.formatHyperlink(Utils.java:600)
at org.zkoss.zss.ui.fn.UtilFns.getCelltext(UtilFns.java:89)
at org.zkoss.zss.ui.Spreadsheet$ExtraCtrl.getCellAttr(Spreadsheet.java:3109)
at org.zkoss.zss.ui.Spreadsheet$ExtraCtrl.getRangeAttrs(Spreadsheet.java:2933)
at org.zkoss.zss.ui.Spreadsheet.createActiveRange(Spreadsheet.java:1680)
at org.zkoss.zss.ui.Spreadsheet.renderProperties(Spreadsheet.java:1653)
at org.zkoss.zk.ui.AbstractComponent.redraw(AbstractComponent.java:1805)
at org.zkoss.zk.ui.sys.HtmlPageRenders.outPageContent(HtmlPageRenders.java:609)
at org.zkoss.zul.impl.PageRenderer.renderDesktop(PageRenderer.java:98)
at org.zkoss.zul.impl.PageRenderer.render(PageRenderer.java:56)
at org.zkoss.zk.ui.impl.PageImpl.redraw(PageImpl.java:854)
at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage0(UiEngineImpl.java:490)
at org.zkoss.zk.ui.impl.UiEngineImpl.execNewPage(UiEngineImpl.java:316)
at org.zkoss.zk.ui.http.DHtmlLayoutServlet.process(DHtmlLayoutServlet.java:215)
at org.zkoss.zk.ui.http.DHtmlLayoutServlet.doGet(DHtmlLayoutServlet.java:135)
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)