NPE when using batchHandler

[Strainy]

Version

v4.5.9

Context

I'm running into the following NPE when specifying a batchHandler on the consumer. Seems like it's still necessary to specify a no-op handler()... even if you just need to use the batchHandler?

java.lang.NullPointerException: Cannot invoke "io.vertx.core.Handler.handle(Object)" because "handler" is null
	at io.vertx.kafka.client.consumer.impl.KafkaReadStreamImpl.lambda$tracedHandler$11(KafkaReadStreamImpl.java:251)
	at io.vertx.kafka.client.consumer.impl.KafkaReadStreamImpl.lambda$run$10(KafkaReadStreamImpl.java:240)
	at io.vertx.core.impl.ContextImpl.emit(ContextImpl.java:328)
	at io.vertx.core.impl.DuplicatedContext.emit(DuplicatedContext.java:164)
	at io.vertx.core.impl.ContextInternal.emit(ContextInternal.java:200)
	at io.vertx.kafka.client.consumer.impl.KafkaReadStreamImpl.run(KafkaReadStreamImpl.java:240)
	at io.vertx.kafka.client.consumer.impl.KafkaReadStreamImpl.lambda$schedule$8(KafkaReadStreamImpl.java:194)
	at io.vertx.core.impl.ContextInternal.dispatch(ContextInternal.java:270)
	at io.vertx.core.impl.ContextInternal.dispatch(ContextInternal.java:252)
	at io.vertx.core.impl.ContextInternal.lambda$runOnContext$0(ContextInternal.java:50)
	at io.vertx.core.impl.WorkerExecutor.lambda$execute$0(WorkerExecutor.java:68)
	at io.vertx.core.impl.TaskQueue.run(TaskQueue.java:76)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1144)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:642)

Do you have a reproducer?

You can see the error logged in the tracing tests if you switch the handler to batchHandler without also specifying a handler, for example:
Strainy@e1030fa

Steps to reproduce

Just use batchHandler without an individual record handler.

Extra

N/A

[Strainy]

Got a fix for the issue here 🙏
#281

[tsegismont]

Fixed by f02269a

[tsegismont]

I had to revert the commits in both the main and the 4.x branches because the build was failing.

@Strainy would you mind creating the PR again ? I hope the test suite can catch the failure

[Strainy]

@tsegismont #284 🙏

[tsegismont]

Fixed by #286