Update for new combinator API

index.js

@@ -27,7 +27,7 @@ function containsRules(rules) {
 }
 
 module.exports = function hasShape(rules) {
-	return combinator((object, applyValidators, context) => {
+	let validator = combinator((object, applyValidators, context) => {
 		let allowExtraProperties = defaultValue(context.allowExtraProperties, false);
 
 		let unexpectedPropertyErrors = asExpression(() => {
@@ -80,4 +80,8 @@ module.exports = function hasShape(rules) {
 			});
 		}
 	});
+
+	validator.callIfNull = false;
+
+	return validator;
 };