[KYUUBI #3297] [MINOR] Null is replaced by KyuubiSQLException.featureNotSupported()

### _Why are the changes needed?_

### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible

- [ ] Add screenshots for manual tests if appropriate

- [ ] [Run test](https://kyuubi.apache.org/docs/latest/develop_tools/testing.html#running-tests) locally before make a pull request

Closes #3297 from zhaomin1423/minor_null.

Closes #3297

9008737 [Min] [MINOR] Null is replaced by KyuubiSQLException.featureNotSupported()

Authored-by: Min <zhaomin1423@163.com>
Signed-off-by: Cheng Pan <chengpan@apache.org>

Author: zhaomin1423

kyuubi-server/src/main/scala/org/apache/kyuubi/operation/KyuubiOperationManager.scala

@@ -21,6 +21,7 @@ import java.util.concurrent.TimeUnit
 
 import org.apache.hive.service.rpc.thrift.TRowSet
 
+import org.apache.kyuubi.KyuubiSQLException
 import org.apache.kyuubi.config.KyuubiConf
 import org.apache.kyuubi.config.KyuubiConf.OPERATION_QUERY_TIMEOUT
 import org.apache.kyuubi.metrics.MetricsConstants.OPERATION_OPEN
@@ -87,19 +88,19 @@ class KyuubiOperationManager private (name: String) extends OperationManager(nam
 
   // The server does not use these 4 operations
   override def newSetCurrentCatalogOperation(session: Session, catalog: String): Operation = {
-    null
+    throw KyuubiSQLException.featureNotSupported()
   }
 
   override def newGetCurrentCatalogOperation(session: Session): Operation = {
-    null
+    throw KyuubiSQLException.featureNotSupported()
   }
 
   override def newSetCurrentDatabaseOperation(session: Session, database: String): Operation = {
-    null
+    throw KyuubiSQLException.featureNotSupported()
   }
 
   override def newGetCurrentDatabaseOperation(session: Session): Operation = {
-    null
+    throw KyuubiSQLException.featureNotSupported()
   }
 
   override def newGetTypeInfoOperation(session: Session): Operation = {