fix: Prevent null reference exceptions while serializing LoadedModuleWireModelCollection. (#2185)

[tippmar-nr]

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Description

Adds defensive coding to prevent null reference exceptions while serializing LoadedModuleWireModelCollection. Improves unit tests to check for null values.

Fixes #2185

Author Checklist

• Unit tests, Integration tests, and Unbounded tests completed
• Performance testing completed with satisfactory results (if required)

Reviewer Checklist

• Perform code review
• Pull request was adequately tested (new/existing tests, performance tests)

[chynesNR]

Ah, now I get why this popped up. Looks good.

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (11c0241) 81.02% compared to head (52d7ede) 81.01%.
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2187      +/-   ##
==========================================
- Coverage   81.02%   81.01%   -0.01%     
==========================================
  Files         396      396              
  Lines       24721    24713       -8     
  Branches     2997     2997              
==========================================
- Hits        20029    20021       -8     
+ Misses       3904     3903       -1     
- Partials      788      789       +1     

Files	Coverage Δ
...rs/LoadedModuleWireModelCollectionJsonConverter.cs	83.33% <0.00%> (-4.17%)	⬇️
...Core/WireModels/LoadedModuleWireModelCollection.cs	99.27% <83.33%> (-0.73%)	⬇️

... and 2 files with indirect coverage changes