Fix test build of nlopt algo

Author: Dave-Poissant

tests/nlopt.cpp

@@ -385,7 +385,8 @@ BOOST_AUTO_TEST_CASE(nlopt_loc_opt)
 BOOST_AUTO_TEST_CASE(nlopt_initial_population_not_respecting_bounds_throw_test)
 {
     // We test that the algorithm throws if the initial population does not respect the bounds
-    auto pop = population{hs71{}, 1};
+    auto prob = hs71{};
+    auto pop = population{prob, 1};
     auto a = nlopt{"slsqp"};
     auto dv = pop.get_x()[0];
     dv[0] = prob.get_bounds().first[0] - 1.;