[Hotfix][Connector-V2] Fix connector source snapshot state NPE (#4027)

Author: hailin0

release-note.md

@@ -45,6 +45,8 @@
 ### Connectors
 - [ClickHouse File] Fix ClickhouseFile Committer Serializable Problems #3803
 - [ClickHouse] Fix clickhouse write cdc changelog update event #3951
+- [ClickHouse] Fix connector source snapshot state NPE #4027
+- [Kudu] Fix connector source snapshot state NPE #4027
 
 ### Zeta Engine
 - [Checkpoint] Fix Checkpoint Continue Trigger After Job CANCELED #3808

seatunnel-connectors-v2/connector-clickhouse/src/main/java/org/apache/seatunnel/connectors/seatunnel/clickhouse/source/ClickhouseSourceReader.java

@@ -31,6 +31,7 @@
 
 import java.io.IOException;
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 import java.util.Random;
 
@@ -88,7 +89,7 @@ public void pollNext(Collector<SeaTunnelRow> output) throws Exception {
 
     @Override
     public List<ClickhouseSourceSplit> snapshotState(long checkpointId) throws Exception {
-        return null;
+        return Collections.emptyList();
     }
 
     @Override

seatunnel-connectors-v2/connector-kudu/src/main/java/org/apache/seatunnel/connectors/seatunnel/kudu/source/KuduSourceReader.java

@@ -29,6 +29,7 @@
 import org.apache.kudu.client.RowResult;
 import org.apache.kudu.client.RowResultIterator;
 
+import java.util.Collections;
 import java.util.Deque;
 import java.util.LinkedList;
 import java.util.List;
@@ -85,7 +86,7 @@ public void pollNext(Collector<SeaTunnelRow> output) throws Exception {
 
     @Override
     public List<KuduSourceSplit> snapshotState(long checkpointId) {
-        return null;
+        return Collections.emptyList();
     }
 
     @Override