unlock place_loc_vars before accessing it

Author: soheilshahrouz

vpr/src/place/place.cpp

@@ -2436,11 +2436,16 @@ static void calculate_reward_and_process_outcome(
 
 static void copy_locs_to_global_state(const PlaceLocVars& place_loc_vars) {
     auto& place_ctx = g_vpr_ctx.mutable_placement();
-    auto& global_place_loc_vars = place_ctx.mutable_place_loc_vars();
 
+    // the placement location variables should be unlocked before being accessed
     place_ctx.unlock_loc_vars();
 
+    // copy the local location variables into the global state
+    auto& global_place_loc_vars = place_ctx.mutable_place_loc_vars();
     global_place_loc_vars = place_loc_vars;
 
+#ifndef NO_GRAPHICS
+    // update the graphics' reference to placement location variables
     set_graphics_place_loc_vars_ref(global_place_loc_vars);
+#endif
 }