Fix: Don't restore backed up vehicle name if it's no longer unique. (#10979)

(cherry picked from commit 2097719f26)

src/order_backup.cpp

@@ -16,6 +16,7 @@
 #include "vehicle_base.h"
 #include "window_func.h"
 #include "station_map.h"
+#include "vehicle_func.h"
 
 #include "safeguards.h"
 
@@ -98,6 +99,9 @@ void OrderBackup::DoRestore(Vehicle *v)
 		InvalidateWindowClassesData(WC_STATION_LIST, 0);
 	}
 
+	/* Remove backed up name if it's no longer unique. */
+	if (!this->name.empty() && !IsUniqueVehicleName(this->name.c_str())) this->name.clear();
+
 	v->CopyConsistPropertiesFrom(this);
 
 	/* Make sure orders are in range */

src/vehicle_cmd.cpp

@@ -827,7 +827,7 @@ CommandCost CmdDepotMassAutoReplace(TileIndex tile, DoCommandFlag flags, uint32
  * @param name Name to test.
  * @return True if the name is unique.
  */
-static bool IsUniqueVehicleName(const char *name)
+bool IsUniqueVehicleName(const char *name)
 {
 	for (const Vehicle *v : Vehicle::Iterate()) {
 		if (!v->name.empty() && v->name == name) return false;

src/vehicle_func.h

@@ -267,4 +267,6 @@ void CheckCargoCapacity(Vehicle *v);
 bool VehiclesHaveSameEngineList(const Vehicle *v1, const Vehicle *v2);
 bool VehiclesHaveSameOrderList(const Vehicle *v1, const Vehicle *v2);
 
+bool IsUniqueVehicleName(const char *name);
+
 #endif /* VEHICLE_FUNC_H */