Fix DeleteVisibleTrain being called on virtual trains

Add assertion to check for this case

src/economy.cpp

@@ -407,7 +407,7 @@ void ChangeOwnershipOfCompanyItems(Owner old_owner, Owner new_owner)
 			if (v->owner == old_owner && IsCompanyBuildableVehicleType(v->type)) {
 				if (new_owner == INVALID_OWNER) {
 					if (v->Previous() == NULL) {
-						if (_settings_game.economy.infrastructure_sharing[VEH_TRAIN] && v->type == VEH_TRAIN && Train::From(v)->IsFrontEngine()) {
+						if (_settings_game.economy.infrastructure_sharing[VEH_TRAIN] && v->type == VEH_TRAIN && Train::From(v)->IsFrontEngine() && !Train::From(v)->IsVirtual()) {
 							DeleteVisibleTrain(Train::From(v));
 						} else {
 							delete v;

src/infrastructure.cpp

@@ -175,7 +175,7 @@ static void RemoveAndSellVehicle(Vehicle *v, bool give_money)
 	}
 
 	/* take special measures for trains, but not when sharing is disabled or when the train is a free wagon chain */
-	if (_settings_game.economy.infrastructure_sharing[VEH_TRAIN] && v->type == VEH_TRAIN && Train::From(v)->IsFrontEngine()) {
+	if (_settings_game.economy.infrastructure_sharing[VEH_TRAIN] && v->type == VEH_TRAIN && Train::From(v)->IsFrontEngine() && !Train::From(v)->IsVirtual()) {
  		DeleteVisibleTrain(Train::From(v));
 	} else {
 		delete v;

src/train_cmd.cpp

@@ -4754,6 +4754,8 @@ void DeleteVisibleTrain(Train *v)
 {
 	SCOPE_INFO_FMT([v], "DeleteVisibleTrain: %s", scope_dumper().VehicleInfo(v));
 
+	assert(!v->IsVirtual());
+
 	FreeTrainTrackReservation(v);
 	TileIndex crossing = TrainApproachingCrossingTile(v);