Make resource identifiers optional
Reported by omero in https://forum.freeciv.org/f/viewtopic.php?t=93876
Resource identifiers are needed only when loading old savegames. Identifiers added since savegame format has changed have no use at all. Make them optional in the ruleset loading code.
Reported by omero in https://forum.freeciv.org/f/viewtopic.php?t=93876
Resource identifiers are needed only when loading old savegames. Identifiers added since savegame format has changed have no use at all. Make them optional in the ruleset loading code.