TBTR: Fix TemplateVehicle allocation check in CmdReplaceTemplateVehicle

src/tbtr_template_vehicle_func.cpp

@@ -175,15 +175,8 @@ void SetupTemplateVehicleFromVirtual(TemplateVehicle *tmp, TemplateVehicle *prev
 // create a full TemplateVehicle based train according to a virtual train
 TemplateVehicle* TemplateVehicleFromVirtualTrain(Train *virt)
 {
-	if (!virt) return nullptr;
-
 	Train *init_virt = virt;
 
-	int len = CountVehiclesInChain(virt);
-	if (!TemplateVehicle::CanAllocateItem(len)) {
-		return nullptr;
-	}
-
 	TemplateVehicle *tmp;
 	TemplateVehicle *prev = nullptr;
 	for (; virt; virt = virt->Next()) {

src/vehicle_cmd.cpp

@@ -1143,6 +1143,10 @@ CommandCost CmdReplaceTemplateVehicle(TileIndex tile, DoCommandFlag flags, uint3
 
 	Train* train = Train::From(vehicle);
 
+	if (!TemplateVehicle::CanAllocateItem(CountVehiclesInChain(train))) {
+		return CMD_ERROR;
+	}
+
 	bool should_execute = (flags & DC_EXEC) != 0;
 
 	if (should_execute) {
@@ -1167,10 +1171,6 @@ CommandCost CmdReplaceTemplateVehicle(TileIndex tile, DoCommandFlag flags, uint3
 
 		template_vehicle = TemplateVehicleFromVirtualTrain(train);
 
-		if (template_vehicle == nullptr) {
-			return CMD_ERROR;
-		}
-
 		if (restore_flags) {
 			template_vehicle->reuse_depot_vehicles = reuse_depot_vehicles;
 			template_vehicle->keep_remaining_vehicles = keep_remaining_vehicles;