Allow null characteristics

Fix to allow null characteristic values - they appear to actually be supported by Homekit

Author: andylintner

src/main/java/com/beowulfe/hap/characteristics/BaseCharacteristic.java

@@ -90,7 +90,7 @@ protected CompletableFuture<JsonObjectBuilder> makeBuilder(int instanceId) {
 				.add("events", false)
 				.add("bonjour", false)
 				.add("description", description);
-			setJsonValue(builder, value != null ? value : getDefault());
+			setJsonValue(builder, value);
 			return builder;
 		});
 	}

src/main/java/com/beowulfe/hap/characteristics/FloatCharacteristic.java

@@ -69,7 +69,7 @@ protected Double convert(JsonValue jsonValue) {
 	@Override
 	protected final CompletableFuture<Double> getValue() {
 		double rounder = 1 / this.minStep;
-		return getDoubleValue().thenApply(d -> Math.round(d * rounder) / rounder); 
+		return getDoubleValue().thenApply(d -> d == null ? null : Math.round(d * rounder) / rounder); 
 	}
 
 	/**