Codechange: make explicit when a TileIndex is cast to its basetype (#11190)

This prevents people accidentially assigning a TileIndex to a Date
or any other type they shouldn't.

src/saveload/afterload.cpp

@@ -2143,7 +2143,7 @@ bool AfterLoadGame()
 		/* Delete small ufos heading for non-existing vehicles */
 		for (DisasterVehicle *v : DisasterVehicle::Iterate()) {
 			if (v->subtype == 2 /* ST_SMALL_UFO */ && v->state != 0) {
-				const Vehicle *u = Vehicle::GetIfValid(v->dest_tile);
+				const Vehicle *u = Vehicle::GetIfValid(static_cast<uint32_t>(v->dest_tile));
 				if (u == nullptr || u->type != VEH_ROAD || !RoadVehicle::From(u)->IsFrontEngine()) {
 					delete v;
 				}