StreamManager: NoSuchElementException

Hi,

we’ve seen this stacktrace in Openfire 4.5.2:

org.jivesoftware.openfire.nio.ConnectionHandler - Closing connection due to error while processing message: <a xmlns="urn:xmpp:sm:3" h="1"/>
java.util.NoSuchElementException: null
        at java.util.LinkedList.getLast(LinkedList.java:261) ~[?:?]
        at org.jivesoftware.openfire.streammanagement.StreamManager.processClientAcknowledgement(StreamManager.java:463) ~[xmppserver-4.5.2.jar:4.5.2]
        at org.jivesoftware.openfire.streammanagement.StreamManager.process(StreamManager.java:164) ~[xmppserver-4.5.2.jar:4.5.2]
        at org.jivesoftware.openfire.net.StanzaHandler.process(StanzaHandler.java:200) ~[xmppserver-4.5.2.jar:4.5.2]
        at org.jivesoftware.openfire.nio.ConnectionHandler.messageReceived(ConnectionHandler.java:183) [xmppserver-4.5.2.jar:4.5.2]
        at org.apache.mina.core.filterchain.DefaultIoFilterChain$TailFilter.messageReceived(DefaultIoFilterChain.java:1015) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:650) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1300(DefaultIoFilterChain.java:49) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:1128) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.IoFilterAdapter.messageReceived(IoFilterAdapter.java:122) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:650) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1300(DefaultIoFilterChain.java:49) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:1128) [mina-core-2.1.3.jar:?]
        at org.apache.mina.filter.codec.ProtocolCodecFilter$ProtocolDecoderOutputImpl.flush(ProtocolCodecFilter.java:413) [mina-core-2.1.3.jar:?]
        at org.apache.mina.filter.codec.ProtocolCodecFilter.messageReceived(ProtocolCodecFilter.java:257) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.DefaultIoFilterChain.callNextMessageReceived(DefaultIoFilterChain.java:650) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.DefaultIoFilterChain.access$1300(DefaultIoFilterChain.java:49) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.DefaultIoFilterChain$EntryImpl$1.messageReceived(DefaultIoFilterChain.java:1128) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.filterchain.IoFilterEvent.fire(IoFilterEvent.java:106) [mina-core-2.1.3.jar:?]
        at org.apache.mina.core.session.IoEvent.run(IoEvent.java:89) [mina-core-2.1.3.jar:?]
        at org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.runTask(OrderedThreadPoolExecutor.java:766) [mina-core-2.1.3.jar:?]
        at org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.runTasks(OrderedThreadPoolExecutor.java:758) [mina-core-2.1.3.jar:?]
        at org.apache.mina.filter.executor.OrderedThreadPoolExecutor$Worker.run(OrderedThreadPoolExecutor.java:697) [mina-core-2.1.3.jar:?]
        at java.lang.Thread.run(Thread.java:834) [?:?]

Any ideas?