Empty `.map` pipeline never completes

[fubuloubu]

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I have a pipeline task that's like Pipeline(broker, produces_array).map(another_task) but it never completes when I want using task.wait_result if produces_array returns an empty list

[fubuloubu]

I think if you just bail here when len is 0, it would work:

https://github.com/taskiq-python/taskiq-pipelines/blob/ba056d7bfc0c46ea1235323c93ed6ec09b64ed41/taskiq_pipelines/steps/mapper.py#L109-L111