NPE trying to kick user from MUC

Hey,

I have a problem kicking a user from a MUC. When initiating the kick client side (MUC Owner), I get the following exception. Any hints?

2012.07.20 12:36:00 org.jivesoftware.openfire.muc.spi.LocalMUCUser -
java.lang.NullPointerException
at org.jivesoftware.openfire.muc.spi.LocalMUCRoom.kickPresence(LocalMUCRoom.java:2 011)
at org.jivesoftware.openfire.muc.spi.LocalMUCRoom.kickOccupant(LocalMUCRoom.java:1 987)
at org.jivesoftware.openfire.muc.spi.IQAdminHandler.handleItemsElement(IQAdminHand ler.java:269)
at org.jivesoftware.openfire.muc.spi.IQAdminHandler.handleIQ(IQAdminHandler.java:9 4)
at org.jivesoftware.openfire.muc.spi.LocalMUCUser.process(LocalMUCUser.java:414)
at org.jivesoftware.openfire.muc.spi.LocalMUCUser.process(LocalMUCUser.java:191)
at org.jivesoftware.openfire.muc.spi.MultiUserChatServiceImpl.processPacket(MultiU serChatServiceImpl.java:321)
at org.jivesoftware.openfire.component.InternalComponentManager$RoutableComponents .process(InternalComponentManager.java:587)
at org.jivesoftware.openfire.spi.RoutingTableImpl.routeToComponent(RoutingTableImp l.java:352)
at org.jivesoftware.openfire.spi.RoutingTableImpl.routePacket(RoutingTableImpl.jav a:237)
at org.jivesoftware.openfire.IQRouter.handle(IQRouter.java:324)
at org.jivesoftware.openfire.IQRouter.route(IQRouter.java:121)
at org.jivesoftware.openfire.spi.PacketRouterImpl.route(PacketRouterImpl.java:76)
at org.jivesoftware.openfire.net.StanzaHandler.processIQ(StanzaHandler.java:337)
at org.jivesoftware.openfire.net.ClientStanzaHandler.processIQ(ClientStanzaHandler .java:93)
at org.jivesoftware.openfire.net.StanzaHandler.process(StanzaHandler.java:302)
at org.jivesoftware.openfire.net.StanzaHandler.process(StanzaHandler.java:194)
at org.jivesoftware.openfire.nio.ConnectionHandler.messageReceived(ConnectionHandl er.java:169)
at org.apache.mina.common.support.AbstractIoFilterChain$TailFilter.messageReceived (AbstractIoFilterChain.java:570)
at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(Ab stractIoFilterChain.java:299)
at org.apache.mina.common.support.AbstractIoFilterChain.access$1100(AbstractIoFilt erChain.java:53)
at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceive d(AbstractIoFilterChain.java:648)
at org.apache.mina.common.IoFilterAdapter.messageReceived(IoFilterAdapter.java:80)
at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(Ab stractIoFilterChain.java:299)
at org.apache.mina.common.support.AbstractIoFilterChain.access$1100(AbstractIoFilt erChain.java:53)
at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceive d(AbstractIoFilterChain.java:648)
at org.apache.mina.filter.codec.support.SimpleProtocolDecoderOutput.flush(SimplePr otocolDecoderOutput.java:58)
at org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecF ilter.java:185)
at org.apache.mina.common.support.AbstractIoFilterChain.callNextMessageReceived(Ab stractIoFilterChain.java:299)
at org.apache.mina.common.support.AbstractIoFilterChain.access$1100(AbstractIoFilt erChain.java:53)
at org.apache.mina.common.support.AbstractIoFilterChain$EntryImpl$1.messageReceive d(AbstractIoFilterChain.java:648)
at org.apache.mina.filter.executor.ExecutorFilter.processEvent(ExecutorFilter.java :239)
at org.apache.mina.filter.executor.ExecutorFilter$ProcessEventsRunnable.run(Execut orFilter.java:283)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java: 886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:662)