NPE problem in IqRouter

Please help me fix the below issue.

java.lang.NullPointerException

at org.jivesoftware.openfire.IQRouter.sendErrorPacket(IQRouter.java:428)

at org.jivesoftware.openfire.IQRouter.routingFailed(IQRouter.java:464)
at org.jivesoftware.openfire.spi.RoutingTableImpl.routePacket(RoutingTableImpl.jav a:254)
at org.jivesoftware.openfire.net.SocketPacketWriteHandler.process(SocketPacketWrit eHandler.java:68)
at org.jivesoftware.openfire.spi.PacketDelivererImpl.deliver(PacketDelivererImpl.j ava:56)
at org.jivesoftware.openfire.nio.NIOConnection.deliver(NIOConnection.java:278)
at org.jivesoftware.openfire.session.LocalClientSession.deliver(LocalClientSession .java:856)
at org.jivesoftware.openfire.session.LocalSession.process(LocalSession.java:282)
at org.jivesoftware.openfire.spi.RoutingTableImpl.routeToLocalDomain(RoutingTableI mpl.java:344)
at org.jivesoftware.openfire.spi.RoutingTableImpl.routePacket(RoutingTableImpl.jav a:238)
at org.jivesoftware.openfire.SessionManager.userBroadcast(SessionManager.java:1051 )
at org.jivesoftware.openfire.roster.Roster.broadcast(Roster.java:685)
at org.jivesoftware.openfire.roster.Roster.deleteRosterItem(Roster.java:486)
at org.jivesoftware.openfire.roster.RosterManager.deleteRoster(RosterManager.java: 142)
at org.jivesoftware.openfire.roster.RosterManager.userDeleting(RosterManager.java: 591)
at org.jivesoftware.openfire.event.UserEventDispatcher.dispatchEvent(UserEventDisp atcher.java:138)
at org.jivesoftware.openfire.user.UserManager.deleteUser(UserManager.java:224)
at org.jivesoftware.openfire.handler.IQRegisterHandler.handleIQ(IQRegisterHandler. java:249)
at org.jivesoftware.openfire.handler.IQHandler.process(IQHandler.java:65)
at org.jivesoftware.openfire.IQRouter.handle(IQRouter.java:377)
at org.jivesoftware.openfire.IQRouter.route(IQRouter.java:124)
at org.jivesoftware.openfire.spi.PacketRouterImpl.route(PacketRouterImpl.java:76)
at org.jivesoftware.openfire.net.StanzaHandler.processIQ(StanzaHandler.java:330)
at org.jivesoftware.openfire.net.ClientStanzaHandler.processIQ(ClientStanzaHandler .java:93)