Fix upstream savegame load for versions 311 and later

src/saveload/upstream/newgrf_sl.cpp

@@ -22,8 +22,10 @@ namespace upstream_sl {
 /** Save and load the mapping between a spec and the NewGRF it came from. */
 static const SaveLoad _newgrf_mapping_desc[] = {
 	SLE_VAR(EntityIDMapping, grfid,         SLE_UINT32),
-	SLE_VAR(EntityIDMapping, entity_id,     SLE_FILE_U8 | SLE_VAR_U16),
-	SLE_VAR(EntityIDMapping, substitute_id, SLE_FILE_U8 | SLE_VAR_U16),
+	SLE_CONDVAR(EntityIDMapping, entity_id,     SLE_FILE_U8 | SLE_VAR_U16, SL_MIN_VERSION,            SLV_EXTEND_ENTITY_MAPPING),
+	SLE_CONDVAR(EntityIDMapping, entity_id,     SLE_UINT16,                SLV_EXTEND_ENTITY_MAPPING, SL_MAX_VERSION),
+	SLE_CONDVAR(EntityIDMapping, substitute_id, SLE_FILE_U8 | SLE_VAR_U16, SL_MIN_VERSION,            SLV_EXTEND_ENTITY_MAPPING),
+	SLE_CONDVAR(EntityIDMapping, substitute_id, SLE_UINT16,                SLV_EXTEND_ENTITY_MAPPING, SL_MAX_VERSION),
 };
 
 /**