[cdc-base] Fix NPE during snpashot scan phase (#1339)

This closes #1122.

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/source/reader/external/JdbcSourceScanFetcher.java

@@ -111,6 +111,7 @@ public class JdbcSourceScanFetcher implements Fetcher<SourceRecord, SourceSplitB
             boolean reachBinlogEnd = false;
             final List<SourceRecord> sourceRecords = new ArrayList<>();
             while (!reachBinlogEnd) {
+                checkReadException();
                 List<DataChangeEvent> batch = queue.poll();
                 for (DataChangeEvent event : batch) {
                     sourceRecords.add(event.getRecord());

flink-cdc-base/src/main/java/com/ververica/cdc/connectors/base/source/reader/external/JdbcSourceStreamFetcher.java

@@ -77,6 +77,7 @@ public class JdbcSourceStreamFetcher implements Fetcher<SourceRecord, SourceSpli
     public void submitTask(FetchTask<SourceSplitBase> fetchTask) {
         this.streamFetchTask = fetchTask;
         this.currentStreamSplit = fetchTask.getSplit().asStreamSplit();
+        configureFilter();
         taskContext.configure(currentStreamSplit);
         this.queue = taskContext.getQueue();
         executor.submit(