Bugfix in RdKafkaProducer:flush() method

[alexbusu-motork]

Avoid TypeError in RdKafkaProducer::flush()

[alexbusu-motork]

It seems there is an issue with localstack deployment, because after the services are up, one of them (the one on port 4576) shuts down. All of the http requests to service healtcheck curl -i http://localhost:4576/_localstack/health will return 404 🤷
What I've tried is to change the localstack image version, by downgrading and upgrading the patch, minor and major versions, but still no luck in having it working.
I notice that this issue happens in other PRs as well.
@makasim @Steveb-p please help with this issue.

[makasim]

@makasim @Steveb-p please help with this issue.

I can review PR and merge green one. Release a new version. That's it. So, don't expect me to fix failing CI.

[alexbusu-motork]

@makasim ok, please let me know - since this is a failing component of testing stage (not related to the code quality/functionality itself) - who could help me with this issue? I mean, who is maintaining the functional tests environment, so we can check together?

[makasim]

Contributors, like you.

[alexbusu-motork]

@makasim please run the workflow. I've brought some changes.