Fix FFT weight matrix for clean_flicker_noise

[melanieclarke]

Closes #9578

Catch bad values in the computed weight matrix for method='fft' in clean_flicker_noise.

Without this fix, the step occasionally sets entire images to NaN. Test data is jw04645006001_03101_00004_nrs1_rate.fits.

Tasks

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  • update or add relevant tests
  • update relevant docstrings and / or docs/ page
  • start a regression test and include a link to the running job (click here for instructions)
    • Do truth files need to be updated ("okified")?
      • after the reviewer has approved these changes, run okify_regtests to update the truth files
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[melanieclarke]

Regression tests:
https://github.com/spacetelescope/RegressionTests/actions/runs/15852736195

All tests passing.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.22%. Comparing base (bebd3be) to head (ba9b54c).
⚠️ Report is 291 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #9585      +/-   ##
==========================================
- Coverage   81.25%   81.22%   -0.04%     
==========================================
  Files         366      368       +2     
  Lines       37427    37501      +74     
==========================================
+ Hits        30413    30459      +46     
- Misses       7014     7042      +28     

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