Add callIfNull support

index.js

@@ -5,9 +5,13 @@ const combinator = require("@validatem/combinator");
 // TODO: Document that this *exposes* context
 
 module.exports = function dynamic(ruleGenerationFunction) {
-	return combinator((value, applyValidators, context) => {
+	let validator = combinator((value, applyValidators, context) => {
 		let rules = ruleGenerationFunction(value, context);
 
 		return applyValidators(value, rules);
 	});
+
+	validator.callIfNull = true;
+
+	return validator;
 };