JDBCScanner throws NPE when data contains nulls

2016-05-11 15:52:26,158 ERROR org.apache.tajo.master.TajoMasterClientService:
Stack Trace:
org.apache.tajo.exception.TajoInternalError: internal error: null
        at org.apache.tajo.master.exec.NonForwardQueryResultFileScanner.nextRowBlock(NonForwardQueryResultFileScanner.java:256)
        at org.apache.tajo.master.TajoMasterClientService$TajoMasterClientProtocolServiceHandler.getQueryResultData(TajoMasterClientService.java:575)
        at org.apache.tajo.ipc.TajoMasterClientProtocol$TajoMasterClientProtocolService$2.callBlockingMethod(TajoMasterClientProtocol.java:681)
        at org.apache.tajo.rpc.BlockingRpcServer$ServerHandler.channelRead0(BlockingRpcServer.java:100)
        at org.apache.tajo.rpc.BlockingRpcServer$ServerHandler.channelRead0(BlockingRpcServer.java:61)
        at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:307)
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:293)
        at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:307)
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:293)
        at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:276)
        at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:263)
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:307)
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:293)
        at io.netty.channel.ChannelInboundHandlerAdapter.channelRead(ChannelInboundHandlerAdapter.java:86)
        at org.apache.tajo.rpc.MonitorServerHandler.channelRead(MonitorServerHandler.java:70)
        at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:307)
        at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:293)
        at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:840)
        at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:131)
        at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:511)
        at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468)
        at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382)
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354)
        at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:112)
        at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.NullPointerException
        at org.apache.tajo.storage.jdbc.JdbcScanner.convertTuple(JdbcScanner.java:228)
        at org.apache.tajo.storage.jdbc.JdbcScanner$ResultSetIterator.next(JdbcScanner.java:306)
        at org.apache.tajo.storage.jdbc.JdbcScanner.next(JdbcScanner.java:121)
        at org.apache.tajo.engine.planner.physical.FullScanIterator.hasNext(FullScanIterator.java:39)
        at org.apache.tajo.engine.planner.physical.SeqScanExec.next(SeqScanExec.java:292)
        at org.apache.tajo.engine.planner.physical.PartitionMergeScanExec.next(PartitionMergeScanExec.java:88)
        at org.apache.tajo.master.exec.NonForwardQueryResultFileScanner$1.run(NonForwardQueryResultFileScanner.java:286)
        at java.util.concurrent.Executors$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)
        ... 1 more