NullPointerException in broker on notification of ZK session end

I'm seeing a lot of this in my logs on a non-controller broker:

2014-04-02 15:42:23,078] ERROR Error handling event ZkEvent[New session
event sent to
kafka.controller.KafkaController$SessionExpirationListener [ at ] 204a18ac]
(org.I0Itec.zkclient.ZkEventThread)
java.lang.NullPointerException
at
kafka.controller.KafkaController$anonfun$onControllerResignation$1.apply$mcV$sp(KafkaController.scala:340)
at
kafka.controller.KafkaController$anonfun$onControllerResignation$1.apply(KafkaController.scala:337)
at
kafka.controller.KafkaController$anonfun$onControllerResignation$1.apply(KafkaController.scala:337)
at kafka.utils.Utils$.inLock(Utils.scala:538)
at
kafka.controller.KafkaController.onControllerResignation(KafkaController.scala:337)
at
kafka.controller.KafkaController$SessionExpirationListener$anonfun$handleNewSession$1.apply$mcZ$sp(KafkaController.scala:1068)
at
kafka.controller.KafkaController$SessionExpirationListener$anonfun$handleNewSession$1.apply(KafkaController.scala:1067)
at
kafka.controller.KafkaController$SessionExpirationListener$anonfun$handleNewSession$1.apply(KafkaController.scala:1067)
at kafka.utils.Utils$.inLock(Utils.scala:538)
at
kafka.controller.KafkaController$SessionExpirationListener.handleNewSession(KafkaController.scala:1067)
at org.I0Itec.zkclient.ZkClient$4.run(ZkClient.java:472)
at org.I0Itec.zkclient.ZkEventThread.run(ZkEventThread.java:71)

Is it associated with KAFKA-1310 or is it something else?

It seems to be coming at the beginning of onControllerResignation, so non
of the other shutdowns get triggered.