Fix #12388: Vehicle::CopyVehicleConfigAndStatistics not releasing uni…

…t number (#12389)

src/train_cmd.cpp

@@ -1336,8 +1336,7 @@ CommandCost CmdMoveRailVehicle(DoCommandFlag flags, VehicleID src_veh, VehicleID
 			}
 			/* Remove stuff not valid anymore for non-front engines. */
 			DeleteVehicleOrders(src);
-			Company::Get(src->owner)->freeunits[src->type].ReleaseID(src->unitnumber);
-			src->unitnumber = 0;
+			src->ReleaseUnitNumber();
 			src->name.clear();
 		}
 

src/vehicle.cpp

@@ -2401,6 +2401,15 @@ void Vehicle::ResetRefitCaps()
 	for (Vehicle *v = this; v != nullptr; v = v->Next()) v->refit_cap = v->cargo_cap;
 }
 
+/**
+ * Release the vehicle's unit number.
+ */
+void Vehicle::ReleaseUnitNumber()
+{
+	Company::Get(this->owner)->freeunits[this->type].ReleaseID(this->unitnumber);
+	this->unitnumber = 0;
+}
+
 /**
  * Handle the loading of the vehicle; when not it skips through dummy
  * orders and does nothing in all other cases.

src/vehicle_base.h

@@ -750,6 +750,8 @@ struct Vehicle : VehiclePool::PoolItem<&_vehicle_pool>, BaseVehicle, BaseConsist
 
 	void ResetRefitCaps();
 
+	void ReleaseUnitNumber();
+
 	/**
 	 * Copy certain configurations and statistics of a vehicle after successful autoreplace/renew
 	 * The function shall copy everything that cannot be copied by a command (like orders / group etc),
@@ -760,6 +762,7 @@ struct Vehicle : VehiclePool::PoolItem<&_vehicle_pool>, BaseVehicle, BaseConsist
 	{
 		this->CopyConsistPropertiesFrom(src);
 
+		this->ReleaseUnitNumber();
 		this->unitnumber = src->unitnumber;
 
 		this->current_order = src->current_order;