[Bug] Empty class member cause NullpointerException

[scwlkq]

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• I had searched in the issues and found no similar issues.

Environment

Mac

EventMesh version

master

What happened

Runtime（Storage：Local Rocketmq ） + Http Source Connector

请求的路径应该是：curl发送请求->CloudEvent->ConnectRecord-> runtime(storage)
然后我发现是在CloudEvent->ConnectRecord转化的过程中position属性为null：

但是关于消息写入的offset和partition这些属性 应该是由storage的相关模块写入，但是我在CloudEventUtil里看到了关于这个的todo？

How to reproduce

run Runtime（Storage：Local Rocketmq ） + Http Source Connector

Debug logs

2024-02-16 00:11:21,099 DEBUG [vert.x-eventloop-thread-0] ZlibCodecFactory(ZlibCodecFactory.java:39) - -Dio.netty.noJdkZlibDecoder: false
2024-02-16 00:11:21,099 DEBUG [vert.x-eventloop-thread-0] ZlibCodecFactory(ZlibCodecFactory.java:42) - -Dio.netty.noJdkZlibEncoder: false
2024-02-16 00:11:21,170 INFO  [vert.x-eventloop-thread-0] HttpSourceConnector(HttpSourceConnector.java:100) - [HttpSourceConnector] Succeed to convert payload into CloudEvent. StatusCode=200
2024-02-16 00:11:21,174 INFO  [pool-3-thread-1] CloudEventUtil(CloudEventUtil.java:69) - handle receive events testdata



Exception in thread "pool-2-thread-1" java.lang.NullPointerException
	at org.apache.eventmesh.openconnect.offsetmgmt.api.storage.OffsetStorageWriterImpl.writeOffset(OffsetStorageWriterImpl.java:57)
	at java.util.HashMap.forEach(HashMap.java:1290)
	at java.util.Collections$UnmodifiableMap.forEach(Collections.java:1507)
	at org.apache.eventmesh.openconnect.SourceWorker.commitOffsets(SourceWorker.java:346)
	at org.apache.eventmesh.openconnect.SourceWorker.startPollAndSend(SourceWorker.java:219)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
	at java.lang.Thread.run(Thread.java:750)

Are you willing to submit PR?

• Yes I am willing to submit a PR!

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[xwm1992]

可以修复一下这个bug，对于http source connector不需要对应的offset，可以对空指针做一个兼容。 @scwlkq