nao consigo baixar plug-ins

aparece esse erro ao visualizar plug-ins disponiveis.

Exceção:

java.lang.NullPointerException
     at java.lang.String.compareTo(String.java:1139)
     at org.jivesoftware.openfire.update.UpdateManager.getNotInstalledPlugins(UpdateManager.java:343)
     at org.jivesoftware.openfire.admin.available_002dplugins_jsp._jspService(available_002dplugins_jsp.java:86)
     at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
     at org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:547)
     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1359)
     at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:118)
     at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:52)
     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1330)
     at org.jivesoftware.util.LocaleFilter.doFilter(LocaleFilter.java:74)
     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1330)
     at org.jivesoftware.util.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:50)
     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1330)
     at org.jivesoftware.admin.PluginFilter.doFilter(PluginFilter.java:78)
     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1330)
     at org.jivesoftware.admin.AuthCheckFilter.doFilter(AuthCheckFilter.java:164)
     at org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1330)
     at org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:478)
     at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:119)
     at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:520)
     at org.eclipse.jetty.server.session.SessionHandler.doHandle(SessionHandler.java:227)
     at org.eclipse.jetty.server.handler.ContextHandler.doHandle(ContextHandler.java:941)
     at org.eclipse.jetty.servlet.ServletHandler.doScope(ServletHandler.java:409)
     at org.eclipse.jetty.server.session.SessionHandler.doScope(SessionHandler.java:186)
     at org.eclipse.jetty.server.handler.ContextHandler.doScope(ContextHandler.java:875)
     at org.eclipse.jetty.server.handler.ScopedHandler.handle(ScopedHandler.java:117)
     at org.eclipse.jetty.server.handler.ContextHandlerCollection.handle(ContextHandlerCollection.java:250)
     at org.eclipse.jetty.server.handler.HandlerCollection.handle(HandlerCollection.java:149)
     at org.eclipse.jetty.server.handler.HandlerWrapper.handle(HandlerWrapper.java:110)
     at org.eclipse.jetty.server.Server.handle(Server.java:349)
     at org.eclipse.jetty.server.HttpConnection.handleRequest(HttpConnection.java:441)
     at org.eclipse.jetty.server.HttpConnection$RequestHandler.headerComplete(HttpConnection.java:919)
     at org.eclipse.jetty.http.HttpParser.parseNext(HttpParser.java:582)
     at org.eclipse.jetty.http.HttpParser.parseAvailable(HttpParser.java:218)
     at org.eclipse.jetty.server.AsyncHttpConnection.handle(AsyncHttpConnection.java:51)
     at org.eclipse.jetty.io.nio.SelectChannelEndPoint.handle(SelectChannelEndPoint.java:586)
     at org.eclipse.jetty.io.nio.SelectChannelEndPoint$1.run(SelectChannelEndPoint.java:44)
     at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:598)
     at org.eclipse.jetty.util.thread.QueuedThreadPool$3.run(QueuedThreadPool.java:533)
     at java.lang.Thread.run(Thread.java:724)