提交任务时，Flink引发NullPointerException。我该如何解决？

Question

几乎我的Flink工作正常，但偶尔在提交工作时Flink会抛出NPE。

为什么Flink扔了NPE，我该如何解决？

请帮帮我。

java.lang.NullPointerException
    at org.apache.flink.util.Preconditions.checkNotNull(Preconditions.java:58)
    at org.apache.flink.runtime.taskmanager.Task.<init>(Task.java:342)
    at org.apache.flink.runtime.taskexecutor.TaskExecutor.submitTask(TaskExecutor.java:546)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.handleRpcInvocation(AkkaRpcActor.java:247)
    at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.handleRpcMessage(AkkaRpcActor.java:162)
    at org.apache.flink.runtime.rpc.akka.AkkaRpcActor.onReceive(AkkaRpcActor.java:142)
    at akka.actor.UntypedActor$$anonfun$receive$1.applyOrElse(UntypedActor.scala:165)
    at akka.actor.Actor$class.aroundReceive(Actor.scala:502)
    at akka.actor.UntypedActor.aroundReceive(UntypedActor.scala:95)
    at akka.actor.ActorCell.receiveMessage(ActorCell.scala:526)
    at akka.actor.ActorCell.invoke(ActorCell.scala:495)
    at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:257)
    at akka.dispatch.Mailbox.run(Mailbox.scala:224)
    at akka.dispatch.Mailbox.exec(Mailbox.scala:234)
    at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
    at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
    at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
    at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)