fix issue #5401 (#5402)

connector/rocketmq-connector/src/main/java/com/alibaba/otter/canal/connector/rocketmq/producer/CanalRocketMQProducer.java

@@ -372,6 +372,10 @@ public class CanalRocketMQProducer extends AbstractMQProducer implements CanalMQ
             topicName = this.defaultMQProducer.withNamespace(topicName);
             DefaultMQProducerImpl innerProducer = this.defaultMQProducer.getDefaultMQProducerImpl();
             TopicPublishInfo topicInfo = innerProducer.getTopicPublishInfoTable().get(topicName);
+            if (topicInfo == null) {
+                innerProducer.getMqClientFactory().updateTopicRouteInfoFromNameServer(topicName);
+            }
+            topicInfo = innerProducer.getTopicPublishInfoTable().get(topicName);
             if (topicInfo == null) {
                 return null;
             } else {