Try fixing compilation error.

Author: breyerml

src/plssvm/svm/csvm.cpp

@@ -228,7 +228,7 @@ std::pair<std::vector<real_type>, real_type> csvm::perform_dimensional_reduction
 
     const std::chrono::steady_clock::time_point dimension_reduction_start_time = std::chrono::steady_clock::now();
 
-    const detail::ssize_t num_rows_reduced = static_cast<ssize_t>(A.num_rows() - 1);
+    const auto num_rows_reduced = static_cast<detail::ssize_t>(A.num_rows() - 1);
 
     // create q_red vector and calculate QA_costs
     std::vector<real_type> q_red(num_rows_reduced);