Fix NPE in amount unit switch.

src/main/lombok/org/leumasjaffe/recipe/model/Amount.java

@@ -47,16 +47,19 @@ public class Amount {
 	@JsonCreator
 	public Amount(final String serial) {
 		final String[] tokens = serial.split(" ", 2);
+		unit = Unit.COUNT;
 		value = Double.parseDouble(tokens[0]);
 		final Optional<Volume> rv = Stream.of(Volume.values())
 				.filter(v -> v.displayName.equals(tokens[1])).findFirst();
 		if (rv.isPresent()) {
+			unit = Unit.VOLUME;
 			vol = rv.get();
 			return;
 		}
 		final Optional<Weight> rw = Stream.of(Weight.values())
 				.filter(w -> w.displayName.equals(tokens[1])).findFirst();
 		if (rw.isPresent()) {
+			unit = Unit.WEIGHT;
 			wgt = rw.get();
 			return;
 		}