Immediately return after fixing column

[Opt-Mucca]

Description

There's an issue with dominatedColumns, where a truly redundant column may be able to be fixed to either its lower or its upper bound, and the code will try to fix to both one-after-another. This raises an error when it tries to fix an already deleted column. The code-fix is to return after fixing the column to one side.

This was found by looking at a failing instance on my clique table changes.

Checklist

• I have read the contributing guidelines
• This PR targets the latest branch
• Tests are passing
• Documentation was updated where relevant
• This PR is not primarily AI-generated (per the AI contributions policy in CONTRIBUTING.md)

[codecov]

Codecov Report

❌ Patch coverage is 84.61538% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 73.33%. Comparing base (4a22cbf) to head (8c63f02).
⚠️ Report is 3 commits behind head on latest.

Files with missing lines	Patch %	Lines
check/TestMipSolver.cpp	83.33%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #3290      +/-   ##
==========================================
- Coverage   73.33%   73.33%   -0.01%     
==========================================
  Files         446      446              
  Lines      108441   108475      +34     
  Branches    17363    17364       +1     
==========================================
+ Hits        79524    79548      +24     
- Misses      28641    28651      +10     
  Partials      276      276              

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[fwesselm]

Sorry, @Opt-Mucca, this is my fault.

Please merge (after making the similar change for the upper bound case)!

EDIT: I can just add this. I hope that is OK.