Method getSelector

src/main/java/fieldbox/boxes/plugins/Planes.java:32–35

(Box root)

	}

	static public Function<Box, Number> getSelector(Box root)
	{
		return root.properties.getOr(selectPlane, () -> null);
	}

	static public double on(Box test, Function<Box, Number> selector) {
		if (selector == null) {