cosbench runs into ArrayIndexOutOfBoundsException on both 0.4.2.c3 and 0.4.2.c4

[atheism]

When ran ceph s3 tests against our own server. we got the following error in system.log.
2016-07-04 09:51:32,568 [ERROR] [AbstractAgent] - unexpected exception
java.lang.ArrayIndexOutOfBoundsException: 0
at com.intel.cosbench.driver.operator.AbstractOperator.errorStatisticsHandle(AbstractOperator.java:117)
at com.intel.cosbench.driver.operator.Reader.doRead(Reader.java:103)
at com.intel.cosbench.driver.operator.Reader.operate(Reader.java:69)
at com.intel.cosbench.driver.operator.AbstractOperator.operate(AbstractOperator.java:76)
at com.intel.cosbench.driver.agent.WorkAgent.performOperation(WorkAgent.java:197)
at com.intel.cosbench.driver.agent.WorkAgent.doWork(WorkAgent.java:177)
at com.intel.cosbench.driver.agent.WorkAgent.execute(WorkAgent.java:134)
at com.intel.cosbench.driver.agent.AbstractAgent.call(AbstractAgent.java:44)
at com.intel.cosbench.driver.agent.AbstractAgent.call(AbstractAgent.java:1)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
2016-07-04 09:51:32,573 [ERROR] [AbstractAgent] - unexpected exception
java.lang.ArrayIndexOutOfBoundsException: 0
at com.intel.cosbench.driver.operator.AbstractOperator.errorStatisticsHandle(AbstractOperator.java:117)
at com.intel.cosbench.driver.operator.Reader.doRead(Reader.java:103)
at com.intel.cosbench.driver.operator.Reader.operate(Reader.java:69)
at com.intel.cosbench.driver.operator.AbstractOperator.operate(AbstractOperator.java:76)
at com.intel.cosbench.driver.agent.WorkAgent.performOperation(WorkAgent.java:197)
at com.intel.cosbench.driver.agent.WorkAgent.doWork(WorkAgent.java:177)
at com.intel.cosbench.driver.agent.WorkAgent.execute(WorkAgent.java:134)
at com.intel.cosbench.driver.agent.AbstractAgent.call(AbstractAgent.java:44)
at com.intel.cosbench.driver.agent.AbstractAgent.call(AbstractAgent.java:1)
at java.util.concurrent.FutureTask.run(FutureTask.java:262)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)

We have written 5000 objects in each bucket. and when we test 100 percent random read to a bucket, the problem occurs and the test is terminated.
The config file used in this test:

<storage type="s3" config="accesskey=ACCESSKEY;secretkey=SECRETKEY;proxyhost=;proxyport=;endpoint=http://192.168.1.182" />

<workstage name="main">
  <work name="main" workers="32" runtime="100">
    <operation type="read" ratio="100" config="cprefix=s3testclone1;containers=u(1,1);objects=u(1,5000)" />
  </work>
</workstage>