java.lang.NullPointerException
	at java.base/java.util.Objects.requireNonNull(Objects.java:221)
	at java.base/java.util.concurrent.ConcurrentLinkedQueue.offer(ConcurrentLinkedQueue.java:355)
	at java.base/java.util.concurrent.ConcurrentLinkedQueue.add(ConcurrentLinkedQueue.java:283)
	at org.jgroups.protocols.pbcast.ViewHandler._add(ViewHandler.java:206)
	at org.jgroups.protocols.pbcast.ViewHandler.add(ViewHandler.java:70)
	at org.jgroups.protocols.pbcast.GMS.up(GMS.java:853)
	at org.jgroups.protocols.pbcast.STABLE.up(STABLE.java:247)
	at org.jgroups.stack.Protocol.up(Protocol.java:299)
	at org.jgroups.protocols.pbcast.NAKACK2.up(NAKACK2.java:583)
	at org.jgroups.protocols.FD_SOCK.suspect(FD_SOCK.java:501)
	at org.jgroups.protocols.FD_SOCK.up(FD_SOCK.java:261)
	at org.jgroups.protocols.MERGE3.up(MERGE3.java:281)
	at org.jgroups.protocols.Discovery.up(Discovery.java:300)
	at org.jgroups.protocols.TP.passMessageUp(TP.java:1400)
	at org.jgroups.util.SubmitToThreadPool$SingleLoopbackHandler.run(SubmitToThreadPool.java:72)

"testng-AsyncBackupTest" #24 prio=5 os_prio=0 cpu=18929.23ms elapsed=489.17s tid=0x00007f0850265800 nid=0x4e751 waiting on condition  [0x00007f07d6cff000]
   java.lang.Thread.State: WAITING (parking)
	at jdk.internal.misc.Unsafe.$$BlockHound$$_park(java.base@11.0.10/Native Method)
	- parking to wait for  <0x00000000c8f7bea8> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
	at jdk.internal.misc.Unsafe.park(java.base@11.0.10/Unsafe.java)
	at java.util.concurrent.locks.LockSupport.park(java.base@11.0.10/LockSupport.java:194)
	at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(java.base@11.0.10/AbstractQueuedSynchronizer.java:2081)
	at org.jgroups.protocols.pbcast.ViewHandler.waitUntilComplete(ViewHandler.java:100)
	at org.jgroups.protocols.pbcast.CoordGmsImpl.leave(CoordGmsImpl.java:50)
	at org.jgroups.protocols.pbcast.GMS.down(GMS.java:1071)
	at org.jgroups.protocols.FlowControl.down(FlowControl.java:303)
	at org.jgroups.protocols.FlowControl.down(FlowControl.java:303)
	at org.jgroups.protocols.FRAG3.down(FRAG3.java:129)
	at org.jgroups.stack.ProtocolStack.down(ProtocolStack.java:921)
	at org.jgroups.JChannel.down(JChannel.java:636)
	at org.jgroups.JChannel.disconnect(JChannel.java:437)
	- locked <0x00000000c8f83478> (a org.jgroups.JChannel)
	at org.jgroups.JChannel._close(JChannel.java:1071)
	at org.jgroups.JChannel.close(JChannel.java:463)
	- locked <0x00000000c8f83478> (a org.jgroups.JChannel)
	at org.jgroups.util.Util.close(Util.java:473)
	at org.jgroups.protocols.relay.Relayer$Bridge.stop(Relayer.java:191)
	at org.jgroups.protocols.relay.Relayer$$Lambda$2936/0x0000000840d64040.accept(Unknown Source)
	at java.util.concurrent.ConcurrentLinkedQueue.forEachFrom(java.base@11.0.10/ConcurrentLinkedQueue.java:1037)
	at java.util.concurrent.ConcurrentLinkedQueue.forEach(java.base@11.0.10/ConcurrentLinkedQueue.java:1054)
	at org.jgroups.protocols.relay.Relayer.stop(Relayer.java:101)
	at org.jgroups.protocols.relay.RELAY2.stop(RELAY2.java:341)
	at org.jgroups.stack.ProtocolStack$$Lambda$1468/0x0000000840acf440.accept(Unknown Source)
	at java.util.ArrayList.forEach(java.base@11.0.10/ArrayList.java:1541)
	at org.jgroups.stack.ProtocolStack.stopStack(ProtocolStack.java:899)
	at org.jgroups.JChannel.stopStack(JChannel.java:1085)
	at org.jgroups.JChannel.disconnect(JChannel.java:444)
	- locked <0x00000000c8fa2510> (a org.jgroups.JChannel)
	at org.infinispan.remoting.transport.jgroups.JGroupsTransport.stop(JGroupsTransport.java:768)
	at org.infinispan.remoting.transport.jgroups.CorePackageImpl$1.stop(CorePackageImpl.java:45)
	at org.infinispan.remoting.transport.jgroups.CorePackageImpl$1.stop(CorePackageImpl.java:27)
	at org.infinispan.factories.impl.BasicComponentRegistryImpl.invokeStop(BasicComponentRegistryImpl.java:665)
	at org.infinispan.factories.impl.BasicComponentRegistryImpl.doStopWrapper(BasicComponentRegistryImpl.java:661)
	at org.infinispan.factories.impl.BasicComponentRegistryImpl.stopWrapper(BasicComponentRegistryImpl.java:649)
	at org.infinispan.factories.impl.BasicComponentRegistryImpl.stop(BasicComponentRegistryImpl.java:516)
	at org.infinispan.factories.AbstractComponentRegistry.internalStop(AbstractComponentRegistry.java:374)
	at org.infinispan.factories.AbstractComponentRegistry.stop(AbstractComponentRegistry.java:308)
	at org.infinispan.manager.DefaultCacheManager.internalStop(DefaultCacheManager.java:820)
	at org.infinispan.manager.DefaultCacheManager.stop(DefaultCacheManager.java:794)
	at org.infinispan.xsite.AbstractXSiteTest$$Lambda$2935/0x0000000840d63c40.accept(Unknown Source)
	at java.util.ArrayList.forEach(java.base@11.0.10/ArrayList.java:1541)
	at org.infinispan.xsite.AbstractXSiteTest.killSite(AbstractXSiteTest.java:103)
	at org.infinispan.xsite.AbstractXSiteTest.killSites(AbstractXSiteTest.java:87)
	at org.infinispan.xsite.AbstractXSiteTest.destroy(AbstractXSiteTest.java:81)