Safely close reporter and clear GPU contexts to avoid UnboundLocalErrors

[IAlibay]

Fixes #1845

Added try/except block to safely close things in case there's an unbound variable.

Checklist

• All new code is appropriately documented (user-facing code must have complete docstrings).
• Added a news entry, or the changes are not user-facing.
• Ran pre-commit: you can run pre-commit locally or comment on this PR with pre-commit.ci autofix.

Manual Tests: these are slow so don't need to be run every commit, only before merging and when relevant changes are made (generally at reviewer-discretion).

• GPU integration tests
• example notebook testing
• packaging tests: run this for any large feature PRs or PRs that add test data.

Developers certificate of origin

• I certify that this contribution is covered by the MIT License here and the Developer Certificate of Origin at https://developercertificate.org/.

[IAlibay]

pre-commit.ci autofix

[github-actions]

No API break detected ✅

[codecov]

Codecov Report

❌ Patch coverage is 53.84615% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 92.96%. Comparing base (89d1948) to head (6eea84d).

Files with missing lines	Patch %	Lines
src/openfe/protocols/openmm_afe/base_afe_units.py	53.84%	6 Missing ⚠️
src/openfe/protocols/openmm_rfe/hybridtop_units.py	53.84%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1846      +/-   ##
==========================================
- Coverage   95.22%   92.96%   -2.27%     
==========================================
  Files         204      204              
  Lines       17623    17629       +6     
==========================================
- Hits        16781    16388     -393     
- Misses        842     1241     +399     

Flag	Coverage Δ
fast-tests	92.96% <53.84%> (?)
slow-tests	?

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