Null object returned from HttpServletRequest getsession

Dear all,

I am getting this error on Production system.please check this trace and tell me the solution.

PortalNode.fireEventOnNode.toEventListener] event=onNodeReadyEvent, target=com.sap.portal.navigation.portallauncher.default, operation failed for com.sap.portal.prt.pom.PortalNode@25081fa3

[EXCEPTION]

java.lang.NullPointerException: while trying to invoke the method javax.servlet.http.HttpSession.getAttribute(java.lang.String) of a null object returned from javax.servlet.http.HttpServletRequest.getSession()

at com.sap.portal.desktop.DesktopService.getValue(DesktopService.java:441)

at com.sap.portal.desktop.DesktopService.getCurrentDesktopUrl(DesktopService.java:1365)

at com.sapportals.portal.navigation.PortalLauncher.doOnNodeReady(PortalLauncher.java:349)

at com.sapportals.portal.prt.component.AbstractPortalComponent.handleEvent(AbstractPortalComponent.java:390)

at com.sap.portal.prt.core.RequestDispatcherFactory$PortalComponentRequestDispatcher$1.service(RequestDispatcherFactory.java:168)

at com.sap.engine.services.servlets_jsp.server.deploy.impl.module.IRequestDispatcherImpl.dispatch(IRequestDispatcherImpl.java:292)

at com.sap.portal.prt.core.RequestDispatcherFactory$PortalComponentRequestDispatcher.handleEvent(RequestDispatcherFactory.java:158)

at com.sap.portal.prt.pom.ComponentNode.handleEvent(ComponentNode.java:242)

at com.sap.portal.prt.pom.PortalNode.fireEventOnNode(PortalNode.java:341)

at com.sapportals.portal.prt.pom.AbstractNode.addChildNode(AbstractNode.java:349)

at com.sap.portal.prt.core.PortalRequestManager.runRequestCycle(PortalRequestManager.java:465)

at com.sapportals.portal.prt.connection.ServletConnection._handleRequest(ServletConnection.java:224)

at com.sapportals.portal.prt.connection.ServletConnection.handleRequest(ServletConnection.java:101)

at com.sap.portal.prt.dispatcher.DispatcherServlet.service(DispatcherServlet.java:132)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)

at com.sap.engine.services.servlets_jsp.server.runtime.FilterChainImpl.runServlet(FilterChainImpl.java:202)

at com.sap.engine.services.servlets_jsp.server.runtime.FilterChainImpl.doFilter(FilterChainImpl.java:103)

at com.sap.portal.prt.dispatcher.CustomHeaderFilter.doFilter(CustomHeaderFilter.java:58)

at com.sap.engine.services.servlets_jsp.server.runtime.FilterChainImpl.doFilter(FilterChainImpl.java:79)

at com.sap.engine.services.servlets_jsp.server.runtime.RequestDispatcherImpl.doWork(RequestDispatcherImpl.java:340)

at com.sap.engine.services.servlets_jsp.server.runtime.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:499)

at com.sap.portal.navigation.Gateway.service(Gateway.java:161)

at javax.servlet.http.HttpServlet.service(HttpServlet.java:847)

at com.sap.engine.services.servlets_jsp.server.runtime.FilterChainImpl.runServlet(FilterChainImpl.java:202)

at com.sap.engine.services.servlets_jsp.server.runtime.FilterChainImpl.doFilter(FilterChainImpl.java:103)

at com.sap.portal.http.EnrichNavRequestFilter.doFilter(EnrichNavRequestFilter.java:49)

at com.sap.engine.services.servlets_jsp.server.runtime.FilterChainImpl.doFilter(FilterChainImpl.java:79)

at com.sap.portal.prt.dispatcher.CustomHeaderFilter.doFilter(CustomHeaderFilter.java:58)

at com.sap.engine.services.servlets_jsp.server.runtime.FilterChainImpl.doFilter(FilterChainImpl.java:79)

at com.sap.engine.services.servlets_jsp.server.HttpHandlerImpl.runServlet(HttpHandlerImpl.java:441)

at com.sap.engine.services.servlets_jsp.server.HttpHandlerImpl.handleRequest(HttpHandlerImpl.java:210)

at com.sap.engine.services.httpserver.server.RequestAnalizer.startServlet(RequestAnalizer.java:441)

at com.sap.engine.services.httpserver.server.RequestAnalizer.startServlet(RequestAnalizer.java:430)

at com.sap.engine.services.servlets_jsp.filters.DSRWebContainerFilter.process(DSRWebContainerFilter.java:38)