Revert "Add callIfNull support"

This reverts commit cb16313b03.

index.js

@@ -20,7 +20,7 @@ function concat(arrays) {
 module.exports = function wrapError(message, rules, options = {}) {
 	let preserveOriginalErrors = defaultValue(options.preserveOriginalErrors, false);
 
-	let validator = combinator((value, applyValidators, context) => {
+	return combinator((value, applyValidators, context) => {
 		let result = applyValidators(value, rules, context);
 
 		if (result.errors.length > 0) {
@@ -76,8 +76,4 @@ module.exports = function wrapError(message, rules, options = {}) {
 			return result;
 		}
 	});
-
-	validator.callIfNull = true;
-
-	return validator;
 };