[SPARK-28644][SQL] Port HIVE-10646: ColumnValue does not handle NULL_TYPE

## What changes were proposed in this pull request?

This PR port [HIVE-10646](https://issues.apache.org/jira/browse/HIVE-10646) to fix Hive 0.12's JDBC client can not handle `NULL_TYPE`:
```sql
Connected to: Hive (version 3.0.0-SNAPSHOT)
Driver: Hive (version 0.12.0)
Transaction isolation: TRANSACTION_REPEATABLE_READ
Beeline version 0.12.0 by Apache Hive
0: jdbc:hive2://localhost:10000> select null;
org.apache.thrift.transport.TTransportException
	at org.apache.thrift.transport.TIOStreamTransport.read(TIOStreamTransport.java:132)
	at org.apache.thrift.transport.TTransport.readAll(TTransport.java:84)
	at org.apache.thrift.transport.TSaslTransport.readLength(TSaslTransport.java:346)
	at org.apache.thrift.transport.TSaslTransport.readFrame(TSaslTransport.java:423)
	at org.apache.thrift.transport.TSaslTransport.read(TSaslTransport.java:405)
```

Server log:
```
19/08/07 09:34:07 ERROR TThreadPoolServer: Error occurred during processing of message.
java.lang.NullPointerException
	at org.apache.hive.service.cli.thrift.TRow$TRowStandardScheme.write(TRow.java:388)
	at org.apache.hive.service.cli.thrift.TRow$TRowStandardScheme.write(TRow.java:338)
	at org.apache.hive.service.cli.thrift.TRow.write(TRow.java:288)
	at org.apache.hive.service.cli.thrift.TRowSet$TRowSetStandardScheme.write(TRowSet.java:605)
	at org.apache.hive.service.cli.thrift.TRowSet$TRowSetStandardScheme.write(TRowSet.java:525)
	at org.apache.hive.service.cli.thrift.TRowSet.write(TRowSet.java:455)
	at org.apache.hive.service.cli.thrift.TFetchResultsResp$TFetchResultsRespStandardScheme.write(TFetchResultsResp.java:550)
	at org.apache.hive.service.cli.thrift.TFetchResultsResp$TFetchResultsRespStandardScheme.write(TFetchResultsResp.java:486)
	at org.apache.hive.service.cli.thrift.TFetchResultsResp.write(TFetchResultsResp.java:412)
	at org.apache.hive.service.cli.thrift.TCLIService$FetchResults_result$FetchResults_resultStandardScheme.write(TCLIService.java:13192)
	at org.apache.hive.service.cli.thrift.TCLIService$FetchResults_result$FetchResults_resultStandardScheme.write(TCLIService.java:13156)
	at org.apache.hive.service.cli.thrift.TCLIService$FetchResults_result.write(TCLIService.java:13107)
	at org.apache.thrift.ProcessFunction.process(ProcessFunction.java:58)
	at org.apache.thrift.TBaseProcessor.process(TBaseProcessor.java:39)
	at org.apache.hive.service.auth.TSetIpAddressProcessor.process(TSetIpAddressProcessor.java:53)
	at org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:310)
	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:819)
```

## How was this patch tested?

unit tests

Closes #25378 from wangyum/SPARK-28644.

Authored-by: Yuming Wang <[email protected]>
Signed-off-by: HyukjinKwon <[email protected]>

Author: wangyum

sql/hive-thriftserver/src/test/scala/org/apache/spark/sql/hive/thriftserver/SparkThriftServerProtocolVersionsSuite.scala

@@ -255,8 +255,7 @@ class SparkThriftServerProtocolVersionsSuite extends HiveThriftJdbcTest {
       }
     }
 
-    // TODO: enable this test case after port HIVE-10646
-    ignore(s"$version get void") {
+    test(s"$version get void") {
       testExecuteStatementWithProtocolVersion(version, "SELECT null") { rs =>
         assert(rs.next())
         assert(rs.getString(1) === null)

sql/hive-thriftserver/v1.2.1/src/main/java/org/apache/hive/service/cli/ColumnValue.java

@@ -205,6 +205,8 @@ public static TColumnValue toTColumnValue(Type type, Object value) {
     case UNION_TYPE:
     case USER_DEFINED_TYPE:
       return stringValue((String)value);
+    case NULL_TYPE:
+      return stringValue((String)value);
     default:
       return null;
     }