Fix NewGRF vehicle variables 4A, FE and FF crashing with virtual trains.

This is due to attempts to look up the rail type of the current tile.

src/newgrf_engine.cpp

@@ -623,6 +623,7 @@ static uint32 VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *object,
 
 		case 0x4A: {
 			if (v->type != VEH_TRAIN) return 0;
+			if (Train::From(v)->IsVirtual()) return 0x1FF;
 			RailType rt = GetTileRailType(v->tile);
 			return (HasPowerOnRail(Train::From(v)->railtype, rt) ? 0x100 : 0) | GetReverseRailTypeTranslation(rt, object->ro.grffile);
 		}
@@ -716,9 +717,14 @@ static uint32 VehicleGetVariable(Vehicle *v, const VehicleScopeResolver *object,
 				const Train *t = Train::From(v);
 				bool is_powered_wagon = HasBit(t->flags, VRF_POWEREDWAGON);
 				const Train *u = is_powered_wagon ? t->First() : t; // for powered wagons the engine defines the type of engine (i.e. railtype)
-				RailType railtype = GetRailType(v->tile);
 				bool powered = t->IsEngine() || is_powered_wagon;
-				bool has_power = HasPowerOnRail(u->railtype, railtype);
+				bool has_power;
+				if (u->IsVirtual()) {
+					has_power = true;
+				} else {
+					RailType railtype = GetRailType(v->tile);
+					has_power = HasPowerOnRail(u->railtype, railtype);
+				}
 
 				if (powered && has_power) SetBit(modflags, 5);
 				if (powered && !has_power) SetBit(modflags, 6);