WindowJoinITCase#testInnerJoin failed on AZP as NPE

Caused by: java.lang.NullPointerException
May 23 02:00:33 	at org.apache.flink.runtime.checkpoint.filemerging.PhysicalFile.deleteIfNecessary(PhysicalFile.java:155)
May 23 02:00:33 	at org.apache.flink.runtime.checkpoint.filemerging.PhysicalFile.decRefCount(PhysicalFile.java:141)
May 23 02:00:33 	at org.apache.flink.runtime.checkpoint.filemerging.LogicalFile.discardWithCheckpointId(LogicalFile.java:118)
May 23 02:00:33 	at org.apache.flink.runtime.checkpoint.filemerging.FileMergingSnapshotManagerBase.discardSingleLogicalFile(FileMergingSnapshotManagerBase.java:574)
May 23 02:00:33 	at org.apache.flink.runtime.checkpoint.filemerging.FileMergingSnapshotManagerBase.discardLogicalFiles(FileMergingSnapshotManagerBase.java:588)
May 23 02:00:33 	at org.apache.flink.runtime.checkpoint.filemerging.FileMergingSnapshotManagerBase.notifyCheckpointAborted(FileMergingSnapshotManagerBase.java:490)
May 23 02:00:33 	at org.apache.flink.runtime.checkpoint.filemerging.WithinCheckpointFileMergingSnapshotManager.notifyCheckpointAborted(WithinCheckpointFileMergingSnapshotManager.java:61)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.SubtaskCheckpointCoordinatorImpl.notifyFileMergingSnapshotManagerCheckpoint(SubtaskCheckpointCoordinatorImpl.java:505)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.SubtaskCheckpointCoordinatorImpl.notifyCheckpoint(SubtaskCheckpointCoordinatorImpl.java:490)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.SubtaskCheckpointCoordinatorImpl.notifyCheckpointAborted(SubtaskCheckpointCoordinatorImpl.java:414)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.StreamTask.lambda$notifyCheckpointAbortAsync$21(StreamTask.java:1513)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.StreamTask.lambda$notifyCheckpointOperation$23(StreamTask.java:1536)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.StreamTaskActionExecutor$1.runThrowing(StreamTaskActionExecutor.java:50)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.mailbox.Mail.run(Mail.java:90)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.runMail(MailboxProcessor.java:398)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.processMailsWhenDefaultActionUnavailable(MailboxProcessor.java:367)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.processMail(MailboxProcessor.java:352)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.mailbox.MailboxProcessor.runMailboxLoop(MailboxProcessor.java:229)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.StreamTask.runMailboxLoop(StreamTask.java:968)
May 23 02:00:33 	at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:917)
May 23 02:00:33 	at org.apache.flink.runtime.taskmanager.Task.runWithSystemExitMonitoring(Task.java:966)
May 23 02:00:33 	at org.apache.flink.runtime.taskmanager.Task.restoreAndInvoke(Task.java:945)
May 23 02:00:33 	at org.apache.flink.runtime.taskmanager.Task.doRun(Task.java:759)
May 23 02:00:33 	at org.apache.flink.runtime.taskmanager.Task.run(Task.java:573)
May 23 02:00:33 	at java.lang.Thread.run(Thread.java:748)