Exception during <a/> propcessing in XEP-0198

2015.12.11 14:41:45 ERROR [socket_c2s-thread-2]: org.jivesoftware.openfire.nio.C
onnectionHandler - Closing connection due to error while processing message: <a
xmlns="urn:xmpp:sm:2" h="424" />
java.util.NoSuchElementException
at java.util.LinkedList.removeFirst(LinkedList.java:270)
at org.jivesoftware.openfire.streammanagement.StreamManager.processClien
tAcknowledgement(StreamManager.java:132)
at org.jivesoftware.openfire.net.StanzaHandler.process(StanzaHandler.jav
a:195)
at org.jivesoftware.openfire.nio.ConnectionHandler.messageReceived(Conne
ctionHandler.java:181)