Fix b0e73277: save/load next_station for CargoPacket again

(cherry picked from commit 9e3763cfb3)

src/saveload/cargopacket_sl.cpp

@@ -29,6 +29,8 @@ SaveLoadTable GetCargoPacketDesc()
 	static const SaveLoad _cargopacket_desc[] = {
 		SLE_VARNAME(CargoPacket, first_station, "source", SLE_UINT16),
 		SLE_VAR(CargoPacket, source_xy,       SLE_UINT32),
+		SLE_CONDVARNAME(CargoPacket, next_hop, "loaded_at_xy", SLE_FILE_U32 | SLE_VAR_U16, SL_MIN_VERSION, SLV_REMOVE_LOADED_AT_XY),
+		SLE_CONDVARNAME(CargoPacket, next_hop, "loaded_at_xy", SLE_UINT16, SLV_REMOVE_LOADED_AT_XY, SL_MAX_VERSION),
 		SLE_VAR(CargoPacket, count,           SLE_UINT16),
 		SLE_CONDVARNAME(CargoPacket, periods_in_transit, "days_in_transit", SLE_FILE_U8 | SLE_VAR_U16, SL_MIN_VERSION, SLV_MORE_CARGO_AGE),
 		SLE_CONDVARNAME(CargoPacket, periods_in_transit, "days_in_transit", SLE_UINT16, SLV_MORE_CARGO_AGE, SLV_PERIODS_IN_TRANSIT_RENAME),

src/saveload/compat/cargopacket_sl_compat.h

@@ -18,7 +18,7 @@ namespace upstream_sl {
 const SaveLoadCompat _cargopacket_sl_compat[] = {
 	SLC_VAR("source"),
 	SLC_VAR("source_xy"),
-	SLC_NULL(4, SL_MIN_VERSION, SLV_REMOVE_LOADED_AT_XY),
+	SLC_VAR("loaded_at_xy"),
 	SLC_VAR("count"),
 	SLC_VAR("days_in_transit"),
 	SLC_VAR("feeder_share"),