Fix 3ac1a2f1e4: Game crash due to invalid vehicle type information. (#14628)

Use std::variant instead of union for vehicle info.

RailVehicleInfo is now non-POD so using in a union causes undefined behaviour.

src/autoreplace_gui.cpp

@@ -145,7 +145,7 @@ class ReplaceVehicleWindow : public Window {
 				case VEH_ROAD:
 					if (draw_left && this->sel_roadtype != INVALID_ROADTYPE) {
 						/* Ensure that the roadtype is specific to the selected one */
-						if (e->u.road.roadtype != this->sel_roadtype) continue;
+						if (e->VehInfo<RoadVehicleInfo>().roadtype != this->sel_roadtype) continue;
 					}
 					break;