NPE in ModelControllerLock

Just noticed this in the host-controller.log while looking into a non-progressing RespawnTestCase:

22:23:50,552 ERROR [org.jboss.as.controller.management-operation] (proxy-threads - 1) JBAS014612: Operation ("register-server") failed - address: ([]): java.lang.NullPointerException
at org.jboss.as.controller.ModelControllerLock$Sync.tryAcquire(ModelControllerLock.java:75) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1220) [rt.jar:1.7.0_15]
at org.jboss.as.controller.ModelControllerLock.lockInterruptibly(ModelControllerLock.java:48) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.controller.ModelControllerImpl.acquireLock(ModelControllerImpl.java:582) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.controller.OperationContextImpl.takeWriteLock(OperationContextImpl.java:403) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.controller.OperationContextImpl.acquireControllerLock(OperationContextImpl.java:700) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.host.controller.mgmt.ServerToHostProtocolHandler$ServerReconnectRequestHandler$1$1.execute(ServerToHostProtocolHandler.java:268)
at org.jboss.as.controller.AbstractOperationContext.executeStep(AbstractOperationContext.java:610) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.controller.AbstractOperationContext.doCompleteStep(AbstractOperationContext.java:488) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.controller.AbstractOperationContext.completeStepInternal(AbstractOperationContext.java:277) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.controller.AbstractOperationContext.executeOperation(AbstractOperationContext.java:272) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.controller.ModelControllerImpl.internalExecute(ModelControllerImpl.java:257) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.controller.AbstractControllerService.internalExecute(AbstractControllerService.java:292) [wildfly-controller-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.host.controller.DomainModelControllerService.access$600(DomainModelControllerService.java:148)
at org.jboss.as.host.controller.DomainModelControllerService$InternalExecutor.execute(DomainModelControllerService.java:899)
at org.jboss.as.host.controller.mgmt.ServerToHostProtocolHandler$ServerReconnectRequestHandler$1.execute(ServerToHostProtocolHandler.java:282)
at org.jboss.as.protocol.mgmt.AbstractMessageHandler$2$1.doExecute(AbstractMessageHandler.java:296) [wildfly-protocol-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at org.jboss.as.protocol.mgmt.AbstractMessageHandler$AsyncTaskRunner.run(AbstractMessageHandler.java:518) [wildfly-protocol-8.0.0.Beta1-SNAPSHOT.jar:8.0.0.Beta1-SNAPSHOT]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [rt.jar:1.7.0_15]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [rt.jar:1.7.0_15]
at java.lang.Thread.run(Thread.java:722) [rt.jar:1.7.0_15]
at org.jboss.threads.JBossThread.run(JBossThread.java:122) [jboss-threads-2.1.0.Final.jar:2.1.0.Final]