Prevent attempting to download from an empty S3 bucket

[theomelo]

Is your feature request related to a problem? Please describe.

Right now, we don't check if the provided S3 is empty before attempting to download the cache.

Describe the solution you'd like

This was a PR proposing this implementation: https://github.com/avmnu-sng/rspec-tracer/pull/55

Describe alternatives you've considered

I believe this change will increase the performance by checking if the bucket is empty before attempting to download the cache.