EventTimeWindowCheckpointingITCase fails with an NPE

May 22 04:35:18 Starting org.apache.flink.test.checkpointing.EventTimeWindowCheckpointingITCase#testTumblingTimeWindow[statebackend type =ROCKSDB_INCREMENTAL_ZK, buffersPerChannel = 2].
org.apache.flink.runtime.client.JobExecutionException: Job execution failed.
	at org.apache.flink.runtime.jobmaster.JobResult.toJobExecutionResult(JobResult.java:144)
	at org.apache.flink.runtime.minicluster.MiniClusterJobClient.lambda$getJobExecutionResult$3(MiniClusterJobClient.java:141)
	at java.util.concurrent.CompletableFuture.uniApply(CompletableFuture.java:616)
	at java.util.concurrent.CompletableFuture$UniApply.tryFire(CompletableFuture.java:591)
	at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:488)
	at java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:1975)
	at org.apache.flink.runtime.rpc.pekko.PekkoInvocationHandler.lambda$invokeRpc$1(PekkoInvocationHandler.java:268)
	at java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:774)
	at java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:750)
	at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:488)
	at java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:1975)
	at org.apache.flink.util.concurrent.FutureUtils.doForward(FutureUtils.java:1287)
	at org.apache.flink.runtime.concurrent.ClassLoadingUtils.lambda$null$1(ClassLoadingUtils.java:93)
	at org.apache.flink.runtime.concurrent.ClassLoadingUtils.runWithContextClassLoader(ClassLoadingUtils.java:68)
	at org.apache.flink.runtime.concurrent.ClassLoadingUtils.lambda$guardCompletionWithContextClassLoader$2(ClassLoadingUtils.java:92)
	at java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:774)
	at java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:750)
	at java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:488)
	at java.util.concurrent.CompletableFuture.complete(CompletableFuture.java:1975)
	at org.apache.flink.runtime.concurrent.pekko.ScalaFutureUtils$1.onComplete(ScalaFutureUtils.java:47)
	at org.apache.pekko.dispatch.OnComplete.internal(Future.scala:310)
	at org.apache.pekko.dispatch.OnComplete.internal(Future.scala:307)
	at org.apache.pekko.dispatch.japi$CallbackBridge.apply(Future.scala:234)
	at org.apache.pekko.dispatch.japi$CallbackBridge.apply(Future.scala:231)
	at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:64)
	at org.apache.flink.runtime.concurrent.pekko.ScalaFutureUtils$DirectExecutionContext.execute(ScalaFutureUtils.java:65)
	at scala.concurrent.impl.CallbackRunnable.executeWithValue(Promise.scala:72)
	at scala.concurrent.impl.Promise$DefaultPromise.$anonfun$tryComplete$1(Promise.scala:288)
	at scala.concurrent.impl.Promise$DefaultPromise.$anonfun$tryComplete$1$adapted(Promise.scala:288)
	at scala.concurrent.impl.Promise$DefaultPromise.tryComplete(Promise.scala:288)
	at org.apache.pekko.pattern.PromiseActorRef.$bang(AskSupport.scala:629)
	at org.apache.pekko.pattern.PipeToSupport$PipeableFuture$$anonfun$pipeTo$1.applyOrElse(PipeToSupport.scala:34)
	at org.apache.pekko.pattern.PipeToSupport$PipeableFuture$$anonfun$pipeTo$1.applyOrElse(PipeToSupport.scala:33)
	at scala.concurrent.Future.$anonfun$andThen$1(Future.scala:536)
	at scala.concurrent.impl.Promise.liftedTree1$1(Promise.scala:33)
	at scala.concurrent.impl.Promise.$anonfun$transform$1(Promise.scala:33)
	at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:64)
	at org.apache.pekko.dispatch.BatchingExecutor$AbstractBatch.processBatch(BatchingExecutor.scala:73)
	at org.apache.pekko.dispatch.BatchingExecutor$BlockableBatch.$anonfun$run$1(BatchingExecutor.scala:110)
	at scala.runtime.java8.JFunction0$mcV$sp.apply(JFunction0$mcV$sp.java:23)
	at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:85)
	at org.apache.pekko.dispatch.BatchingExecutor$BlockableBatch.run(BatchingExecutor.scala:110)
	at org.apache.pekko.dispatch.TaskInvocation.run(AbstractDispatcher.scala:59)
	at org.apache.pekko.dispatch.ForkJoinExecutorConfigurator$PekkoForkJoinTask.exec(ForkJoinExecutorConfigurator.scala:57)
	at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
	at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
	at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
	at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:175)
Caused by: org.apache.flink.runtime.JobException: Recovery is suppressed by FixedDelayRestartBackoffTimeStrategy(maxNumberRestartAttempts=1, backoffTimeMS=0)
	at org.apache.flink.runtime.executiongraph.failover.ExecutionFailureHandler.handleFailure(ExecutionFailureHandler.java:219)
	at org.apache.flink.runtime.executiongraph.failover.ExecutionFailureHandler.handleFailureAndReport(ExecutionFailureHandler.java:166)
	at org.apache.flink.runtime.executiongraph.failover.ExecutionFailureHandler.getFailureHandlingResult(ExecutionFailureHandler.java:121)
	at org.apache.flink.runtime.scheduler.DefaultScheduler.recordTaskFailure(DefaultScheduler.java:279)
	at org.apache.flink.runtime.scheduler.DefaultScheduler.handleTaskFailure(DefaultScheduler.java:270)
	at org.apache.flink.runtime.scheduler.DefaultScheduler.onTaskFailed(DefaultScheduler.java:263)
	at org.apache.flink.runtime.scheduler.SchedulerBase.onTaskExecutionStateUpdate(SchedulerBase.java:788)
	at org.apache.flink.runtime.scheduler.SchedulerBase.updateTaskExecutionState(SchedulerBase.java:765)
	at org.apache.flink.runtime.scheduler.SchedulerNG.updateTaskExecutionState(SchedulerNG.java:83)
	at org.apache.flink.runtime.jobmaster.JobMaster.updateTaskExecutionState(JobMaster.java:496)
	at sun.reflect.GeneratedMethodAccessor18.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.flink.runtime.rpc.pekko.PekkoRpcActor.lambda$handleRpcInvocation$1(PekkoRpcActor.java:318)
	at org.apache.flink.runtime.concurrent.ClassLoadingUtils.runWithContextClassLoader(ClassLoadingUtils.java:83)
	at org.apache.flink.runtime.rpc.pekko.PekkoRpcActor.handleRpcInvocation(PekkoRpcActor.java:316)
	at org.apache.flink.runtime.rpc.pekko.PekkoRpcActor.handleRpcMessage(PekkoRpcActor.java:229)
	at org.apache.flink.runtime.rpc.pekko.FencedPekkoRpcActor.handleRpcMessage(FencedPekkoRpcActor.java:88)
	at org.apache.flink.runtime.rpc.pekko.PekkoRpcActor.handleMessage(PekkoRpcActor.java:174)
	at org.apache.pekko.japi.pf.UnitCaseStatement.apply(CaseStatements.scala:33)
	at org.apache.pekko.japi.pf.UnitCaseStatement.apply(CaseStatements.scala:29)
	at scala.PartialFunction.applyOrElse(PartialFunction.scala:127)
	at scala.PartialFunction.applyOrElse$(PartialFunction.scala:126)
	at org.apache.pekko.japi.pf.UnitCaseStatement.applyOrElse(CaseStatements.scala:29)
	at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:175)
	at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:176)
	at scala.PartialFunction$OrElse.applyOrElse(PartialFunction.scala:176)
	at org.apache.pekko.actor.Actor.aroundReceive(Actor.scala:547)
	at org.apache.pekko.actor.Actor.aroundReceive$(Actor.scala:545)
	at org.apache.pekko.actor.AbstractActor.aroundReceive(AbstractActor.scala:229)
	at org.apache.pekko.actor.ActorCell.receiveMessage(ActorCell.scala:590)
	at org.apache.pekko.actor.ActorCell.invoke(ActorCell.scala:557)
	at org.apache.pekko.dispatch.Mailbox.processMailbox(Mailbox.scala:280)
	at org.apache.pekko.dispatch.Mailbox.run(Mailbox.scala:241)
	at org.apache.pekko.dispatch.Mailbox.exec(Mailbox.scala:253)
	... 4 more
Caused by: java.lang.NullPointerException
	at org.apache.flink.runtime.checkpoint.filemerging.PhysicalFile.deleteIfNecessary(PhysicalFile.java:155)
	at org.apache.flink.runtime.checkpoint.filemerging.PhysicalFile.decRefCount(PhysicalFile.java:141)
	at org.apache.flink.runtime.checkpoint.filemerging.LogicalFile.discardWithCheckpointId(LogicalFile.java:118)
	at org.apache.flink.runtime.checkpoint.filemerging.FileMergingSnapshotManagerBase.discardSingleLogicalFile(FileMergingSnapshotManagerBase.java:574)
	at org.apache.flink.runtime.checkpoint.filemerging.FileMergingSnapshotManagerBase.discardLogicalFiles(FileMergingSnapshotManagerBase.java:588)
	at org.apache.flink.runtime.checkpoint.filemerging.FileMergingSnapshotManagerBase.notifyCheckpointAborted(FileMergingSnapshotManagerBase.java:490)
	at org.apache.flink.runtime.checkpoint.filemerging.WithinCheckpointFileMergingSnapshotManager.notifyCheckpointAborted(WithinCheckpointFileMergingSnapshotManager.java:61)
	at org.apache.flink.streaming.runtime.tasks.SubtaskCheckpointCoordinatorImpl.notifyFileMergingSnapshotManagerCheckpoint(SubtaskCheckpointCoordinatorImpl.java:505)
	at org.apache.flink.streaming.runtime.tasks.SubtaskCheckpointCoordinatorImpl.notifyCheckpoint(SubtaskCheckpointCoordinatorImpl.java:490)
	at org.apache.flink.streaming.runtime.tasks.SubtaskCheckpointCoordinatorImpl.notifyCheckpointAborted(SubtaskCheckpointCoordinatorImpl.java:414)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.lambda$notifyCheckpointAbortAsync$21(StreamTask.java:1513)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.lambda$notifyCheckpointOperation$23(StreamTask.java:1536)
	at org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$1.runThrowing(StreamTaskActionExecutor.java:50)
	at org.apache.flink.streaming.runtime.tasks.mailbox.Mail.run(Mail.java:90)
	at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.runMail(MailboxProcessor.java:398)
	at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.processMailsWhenDefaultActionUnavailable(MailboxProcessor.java:367)
	at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.processMail(MailboxProcessor.java:352)
	at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.runMailboxLoop(MailboxProcessor.java:229)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.afterInvoke(StreamTask.java:998)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:923)
	at org.apache.flink.runtime.taskmanager.Task.runWithSystemExitMonitoring(Task.java:966)
	at org.apache.flink.runtime.taskmanager.Task.restoreAndInvoke(Task.java:945)
	at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:759)
	at org.apache.flink.runtime.taskmanager.Task.run(Task.java:573)
	at java.lang.Thread.run(Thread.java:750)