Fix catalog freeing

[gbrgr]

Since Catalog became a struct (it was a pointer before), we need to adapt freeing a bit.

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 83.87%. Comparing base (f6b0bcb) to head (e7cce39).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
src/catalog.jl	75.00%	1 Missing ⚠️
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Additional details and impacted files

@@            Coverage Diff             @@
##             main      #43      +/-   ##
==========================================
+ Coverage   83.84%   83.87%   +0.03%     
==========================================
  Files           5        5              
  Lines         359      366       +7     
==========================================
+ Hits          301      307       +6     
- Misses         58       59       +1     

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