JP-3584-bugfix: fixed failed save for intermediate (median) files

[emolter]

Resolves JP-3584

Closes #8378

This PR fixes a bug in implementation of JP-3584 that was causing crashes when save_intermediate_results was set True for TSO data.

Checklist for PR authors (skip items if you don't have permissions or they are not applicable)

• [x] added entry in CHANGES.rst within the relevant release section
• [x] updated or added relevant tests
• [x] updated relevant documentation
• [x] added relevant milestone
• [x] added relevant label(s)
• [x] ran regression tests, post a link to the Jenkins job below. How to run regression tests on a PR
• [ ] All comments are resolved
• [ ] Make sure the JIRA ticket is resolved properly

[emolter]

regression tests started here

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 50.00000% with 1 line in your changes missing coverage. Please review.

Project coverage is 58.52%. Comparing base (b7e0b10) to head (30836b0). Report is 337 commits behind head on master.

Files with missing lines	Patch %	Lines
jwst/outlier_detection/outlier_detection_tso.py	50.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #8555 +/- ## ========================================== + Coverage 58.02% 58.52% +0.50% ========================================== Files 388 388 Lines 38977 38958 -19 ========================================== + Hits 22617 22802 +185 + Misses 16360 16156 -204 ```

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