[SBN READ] Fix NPE when check the block location of empty directory

org.apache.hadoop.ipc.RemoteException(java.lang.NullPointerException): java.lang.NullPointerException

	at org.apache.hadoop.ipc.Client.getRpcResponse(Client.java:1554)
	at org.apache.hadoop.ipc.Client.call(Client.java:1492)
	at org.apache.hadoop.ipc.Client.call(Client.java:1389)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:233)
	at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:118)
	at com.sun.proxy.$Proxy12.getListing(Unknown Source)
	at org.apache.hadoop.hdfs.protocolPB.ClientNamenodeProtocolTranslatorPB.getListing(ClientNamenodeProtocolTranslatorPB.java:678)
	at sun.reflect.GeneratedMethodAccessor4.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at org.apache.hadoop.io.retry.RetryInvocationHandler.invokeMethod(RetryInvocationHandler.java:422)
	at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeMethod(RetryInvocationHandler.java:165)
	at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invoke(RetryInvocationHandler.java:157)
	at org.apache.hadoop.io.retry.RetryInvocationHandler$Call.invokeOnce(RetryInvocationHandler.java:95)
	at org.apache.hadoop.io.retry.RetryInvocationHandler.invoke(RetryInvocationHandler.java:359)
	at com.sun.proxy.$Proxy13.getListing(Unknown Source)
	at org.apache.hadoop.hdfs.DFSClient.listPaths(DFSClient.java:1671)
	at org.apache.hadoop.hdfs.DistributedFileSystem$DirListingIterator.(DistributedFileSystem.java:1212)
	at org.apache.hadoop.hdfs.DistributedFileSystem$DirListingIterator.(DistributedFileSystem.java:1195)
	at org.apache.hadoop.hdfs.DistributedFileSystem$25.doCall(DistributedFileSystem.java:1140)
	at org.apache.hadoop.hdfs.DistributedFileSystem$25.doCall(DistributedFileSystem.java:1136)
	at org.apache.hadoop.fs.FileSystemLinkResolver.resolve(FileSystemLinkResolver.java:81)
	at org.apache.hadoop.hdfs.DistributedFileSystem.listLocatedStatus(DistributedFileSystem.java:1154)
	at org.apache.hadoop.fs.FileSystem.listLocatedStatus(FileSystem.java:2054)
	at org.apache.hadoop.mapred.FileInputFormat.singleThreadedListStatus(FileInputFormat.java:278)
	at org.apache.hadoop.mapred.FileInputFormat.listStatus(FileInputFormat.java:239)
	at org.apache.hadoop.mapred.FileInputFormat.getSplits(FileInputFormat.java:325)
	at org.apache.hadoop.hive.ql.io.HiveInputFormat.addSplitsForGroup(HiveInputFormat.java:306)
	at org.apache.hadoop.hive.ql.io.HiveInputFormat.getSplits(HiveInputFormat.java:408)
	at org.apache.hadoop.hive.ql.exec.tez.HiveSplitGenerator.initialize(HiveSplitGenerator.java:159)
	at org.apache.tez.dag.app.dag.RootInputInitializerManager$InputInitializerCallable$1.run(RootInputInitializerManager.java:279)
	at org.apache.tez.dag.app.dag.RootInputInitializerManager$InputInitializerCallable$1.run(RootInputInitializerManager.java:270)
	at java.security.AccessController.doPrivileged(Native Method)
	at javax.security.auth.Subject.doAs(Subject.java:422)
	at org.apache.hadoop.security.UserGroupInformation.doAs(UserGroupInformation.java:1730)
	at org.apache.tez.dag.app.dag.RootInputInitializerManager$InputInitializerCallable.call(RootInputInitializerManager.java:270)
	at org.apache.tez.dag.app.dag.RootInputInitializerManager$InputInitializerCallable.call(RootInputInitializerManager.java:254)
	at com.google.common.util.concurrent.TrustedListenableFutureTask$TrustedFutureInterruptibleTask.runInterruptibly(TrustedListenableFutureTask.java:125)
	at com.google.common.util.concurrent.InterruptibleTask.run(InterruptibleTask.java:57)
	at com.google.common.util.concurrent.TrustedListenableFutureTask.run(TrustedListenableFutureTask.java:78)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:748)