ArrayIndexOutOfBoundsException when performing aggregation on an union block

default> select sum(t.cnt) as cnt, l_orderkey, l_partkey from (
select l_orderkey, l_partkey, CAST(COUNT(1) AS INT4) as cnt from lineitem_small group by l_orderkey, l_partkey 
union all 
select l_orderkey, l_partkey, l_linenumber from lineitem) as t 
group by l_orderkey, l_partkey;

2016-02-18 15:49:37,162 WARN: org.apache.tajo.catalog.statistics.StatisticsUtil (aggregateTableStat(136)) - 3
java.lang.ArrayIndexOutOfBoundsException: 3
    at org.apache.tajo.catalog.statistics.StatisticsUtil.aggregateTableStat(StatisticsUtil.java:125)
    at org.apache.tajo.querymaster.Repartitioner.computeChildBlocksStats(Repartitioner.java:627)
    at org.apache.tajo.querymaster.Repartitioner.scheduleHashShuffledFetches(Repartitioner.java:899)
    at org.apache.tajo.querymaster.Repartitioner.scheduleFragmentsForNonLeafTasks(Repartitioner.java:611)
    at org.apache.tajo.querymaster.Stage$InitAndRequestContainer.schedule(Stage.java:1062)
    at org.apache.tajo.querymaster.Stage$InitAndRequestContainer.access$900(Stage.java:839)
    at org.apache.tajo.querymaster.Stage$InitAndRequestContainer$1.run(Stage.java:865)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
2016-02-18 15:49:37,162 WARN: org.apache.tajo.catalog.statistics.StatisticsUtil (aggregateTableStat(136)) - 4
java.lang.ArrayIndexOutOfBoundsException: 4
    at org.apache.tajo.catalog.statistics.StatisticsUtil.aggregateTableStat(StatisticsUtil.java:125)
    at org.apache.tajo.querymaster.Repartitioner.computeChildBlocksStats(Repartitioner.java:627)
    at org.apache.tajo.querymaster.Repartitioner.scheduleHashShuffledFetches(Repartitioner.java:899)
    at org.apache.tajo.querymaster.Repartitioner.scheduleFragmentsForNonLeafTasks(Repartitioner.java:611)
    at org.apache.tajo.querymaster.Stage$InitAndRequestContainer.schedule(Stage.java:1062)
    at org.apache.tajo.querymaster.Stage$InitAndRequestContainer.access$900(Stage.java:839)
    at org.apache.tajo.querymaster.Stage$InitAndRequestContainer$1.run(Stage.java:865)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
2016-02-18 15:49:37,163 WARN: org.apache.tajo.catalog.statistics.StatisticsUtil (aggregateTableStat(136)) - 5
java.lang.ArrayIndexOutOfBoundsException: 5
    at org.apache.tajo.catalog.statistics.StatisticsUtil.aggregateTableStat(StatisticsUtil.java:125)
    at org.apache.tajo.querymaster.Repartitioner.computeChildBlocksStats(Repartitioner.java:627)
    at org.apache.tajo.querymaster.Repartitioner.scheduleHashShuffledFetches(Repartitioner.java:899)
    at org.apache.tajo.querymaster.Repartitioner.scheduleFragmentsForNonLeafTasks(Repartitioner.java:611)
    at org.apache.tajo.querymaster.Stage$InitAndRequestContainer.schedule(Stage.java:1062)
    at org.apache.tajo.querymaster.Stage$InitAndRequestContainer.access$900(Stage.java:839)
    at org.apache.tajo.querymaster.Stage$InitAndRequestContainer$1.run(Stage.java:865)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
...