(svn r14324) -Fix [FS#2241]: free any blocks that a helicopter may have on an oilrig when the helicopter gets forcefully removed (bankruptcy). For other airports this isn't needed as they can't be used by multiple companies.

src/vehicle.cpp

@@ -651,6 +651,11 @@ void Vehicle::PreDestructor()
 	}
 
 	if (this->type == VEH_ROAD) ClearSlot(this);
+	if (this->type == VEH_AIRCRAFT && this->IsPrimaryVehicle()) {
+		Station *st = GetStation(this->u.air.targetairport);
+		const AirportFTA *layout = st->Airport()->layout;
+		CLRBITS(st->airport_flags, layout[this->u.air.previous_pos].block | layout[this->u.air.pos].block);
+	}
 
 	if (this->type != VEH_TRAIN || (this->type == VEH_TRAIN && (IsFrontEngine(this) || IsFreeWagon(this)))) {
 		InvalidateWindowData(WC_VEHICLE_DEPOT, this->tile);