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?

• [x] Bug fix (fixes an issue).

Checklist

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

• [x] I have read the CONTRIBUTING.md guidelines.
• [x] My code follows the style guidelines of this project.
• [x] I have performed a self-review of my own code.
• [x] I have commented my code, particularly in hard-to-understand areas.
• [x] I have made corresponding changes to the documentation.
• [x] My changes generate no new warnings.
• [x] 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.
• [x] 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 :warning:

Additional details and impacted files

```diff @@ 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](https://app.codecov.io/gh/cytomining/pycytominer/pull/385/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cytomining) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/cytomining/pycytominer/pull/385/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cytomining) | `94.93% <75.00%> (-0.03%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=cytomining#carryforward-flags-in-the-pull-request-comment) to find out more.

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