(svn r9718) -Fix: Don't allow building of rail vehicles whose railtype isn't available yet. This also affects the rail purchase window.

src/engine.cpp

@@ -401,6 +401,12 @@ bool IsEngineBuildable(EngineID engine, byte type, PlayerID player)
 	/* check if it's available */
 	if (!HASBIT(e->player_avail, player)) return false;
 
+	if (type == VEH_TRAIN) {
+		/* Check if the rail type is available to this player */
+		const Player *p = GetPlayer(player);
+		if (!HASBIT(p->avail_railtypes, RailVehInfo(engine)->railtype)) return false;
+	}
+
 	return true;
 }