mip: Fix use-after-move in HighsLpRelaxation::loadModel

[stratakis]

Save lpmodel.num_col_ before passing lpmodel via std::move to lpsolver.passModel(). After the move, lpmodel is in a valid but unspecified state, making access to its members undefined behavior.

Found by Coverity static analysis.

[stratakis]

The was uncovered during a Coverity scan on scipy:

 4. scipy-1.16.2/subprojects/highs/src/mip/HighsLpRelaxation.cpp:227:3: move: "lpmodel" is moved (indicated by "std::move(lpmodel)").
5. scipy-1.16.2/subprojects/highs/src/mip/HighsLpRelaxation.cpp:228:3: use_after_move: "lpmodel" is used after it has been already moved.
   226|     lpsolver.clearModel();
   227|     lpsolver.passModel(std::move(lpmodel));
   228|->   colLbBuffer.resize(lpmodel.num_col_);
   229|     colUbBuffer.resize(lpmodel.num_col_);
   230|   }

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.33%. Comparing base (c29f3ed) to head (eedc74e).
⚠️ Report is 387 commits behind head on latest.

Additional details and impacted files

@@            Coverage Diff             @@
##           latest    #2713      +/-   ##
==========================================
+ Coverage   81.06%   81.33%   +0.26%     
==========================================
  Files         347      349       +2     
  Lines       85219    86135     +916     
==========================================
+ Hits        69083    70054     +971     
+ Misses      16136    16081      -55     

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[jajhall]

This isn't known to have caused any problems, bit it does no harm