Fix overflow detection

Author: filikat

highs/ipm/hipo/ipm/FactorHiGHSSolver.cpp

@@ -34,7 +34,7 @@ static Int getASstructure(const HighsSparseMatrix& A, std::vector<Int>& ptr,
   Int mA = A.num_row_;
   Int nzA = A.numNz();
 
-  if (nA + nzA + mA > kHighsIInf) return kStatusOverflow;
+  if ((int64_t)nA + nzA + mA > (int64_t)kHighsIInf) return kStatusOverflow;
 
   ptr.resize(nA + mA + 1);
   rows.resize(nA + nzA + mA);