我在amazon emr上运行了一个pig作业，但它突然停止工作，出现以下错误：

Pig Stack Trace
---------------
ERROR 2017: Internal error creating job configuration.

org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.JobCreationException: ERROR 2017: Internal error creating job configuration.
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.JobControlCompiler.getJob(JobControlCompiler.java:855)
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.JobControlCompiler.compile(JobControlCompiler.java:294)
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.MapReduceLauncher.launchPig(MapReduceLauncher.java:177)
    at org.apache.pig.PigServer.launchPlan(PigServer.java:1264)
    at org.apache.pig.PigServer.executeCompiledLogicalPlan(PigServer.java:1249)
    at org.apache.pig.PigServer.execute(PigServer.java:1239)
    at org.apache.pig.PigServer.executeBatch(PigServer.java:333)
    at org.apache.pig.tools.grunt.GruntParser.executeBatch(GruntParser.java:137)
    at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:198)
    at org.apache.pig.tools.grunt.GruntParser.parseStopOnError(GruntParser.java:170)
    at org.apache.pig.tools.grunt.Grunt.exec(Grunt.java:84)
    at org.apache.pig.Main.run(Main.java:479)
    at org.apache.pig.Main.main(Main.java:159)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:606)
    at org.apache.hadoop.util.RunJar.main(RunJar.java:187)
Caused by: java.lang.NullPointerException
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.JobControlCompiler.adjustNumReducers(JobControlCompiler.java:875)
    at org.apache.pig.backend.hadoop.executionengine.mapReduceLayer.JobControlCompiler.getJob(JobControlCompiler.java:480)
    ... 17 more
================================================================================

有没有人知道为什么或者可能是什么问题？这是我见过的最模糊的错误之一。