Method asMap_new

src/main/java/fieldbox/boxes/Box.java:897–901

(Object a)

			return from.properties.computeIfAbsent(storageProperty, (k) -> autoconstructor.apply(from))
				.asMap_set(p, o);
		}

		@Override
		public Object asMap_new(Object a) {
			return from.properties.getOrConstruct(storageProperty)
				.asMap_new(a);
		}