fix(greedy-balancer) benign but unnecessary race setting marker from …

…multiple threads

kaminpar-shm/refinement/balancer/greedy_balancer.cc

@@ -116,8 +116,8 @@ BlockWeight GreedyBalancer::perform_round() {
           _p_graph->adjacent_nodes(u, [&](const NodeID v) {
             if (!_marker.get(v) && _p_graph->block(v) == from) {
               add_to_pq(from, v);
+              _marker.set(v);
             }
-            _marker.set(v);
           });
         } else {
           add_to_pq(from, u, u_weight, actual_relative_gain);