Check if downloaded file is empty

[shntnu]

Description

We must check if the downloaded file (from S3) exists and has a size greater than 0

What is the nature of your change?

• Bug fix (fixes an issue).

Checklist

Please ensure that all boxes are checked before indicating that a pull request is ready for review.

• I have read the CONTRIBUTING.md guidelines.
• My code follows the style guidelines of this project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• New and existing unit tests pass locally with my changes.
• I have added tests that prove my fix is effective or that my feature works. Did not do this because would need mocking S3.
• I have deleted all non-relevant text in this pull request template.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 75.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 94.93%. Comparing base (16f3500) to head (5679991).

Files	Patch %	Lines
pycytominer/cyto_utils/cell_locations.py	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #385      +/-   ##
==========================================
- Coverage   94.96%   94.93%   -0.03%     
==========================================
  Files          56       56              
  Lines        3137     3140       +3     
==========================================
+ Hits         2979     2981       +2     
- Misses        158      159       +1     

Flag	Coverage Δ
unittests	94.93% <75.00%> (-0.03%)	⬇️

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