[C++] Use const ref in urdf geometry parser

src/multibody/parser/urdf-with-geometry.hxx

@@ -124,7 +124,7 @@
         {
           fcl::CollisionObject collision_object = retrieveCollisionGeometry((*i)->geometry, package_dirs, mesh_path);
           SE3 geomPlacement = convertFromUrdf((*i)->origin);
-          std::string collision_object_name = link_name;
+          const std::string & collision_object_name = link_name;
           geom_model.addCollisionObject(model.getFrameParent(link_name), collision_object, geomPlacement, collision_object_name, mesh_path); 
         }
       } // if(link->collision)
@@ -142,7 +142,7 @@
         {
           fcl::CollisionObject visual_object = retrieveCollisionGeometry((*i)->geometry, package_dirs, mesh_path);
           SE3 geomPlacement = convertFromUrdf((*i)->origin);
-          std::string visual_object_name = link_name;
+          const std::string & visual_object_name = link_name;
           geom_model.addVisualObject(model.getFrameParent(link_name), visual_object, geomPlacement, visual_object_name, mesh_path); 
         }
       } // if(link->visual)