Add missing default for `options`

src/index.js

@@ -29,7 +29,7 @@ function reachedRoot(candidatePath) {
 	return /^(?:\/|[a-z]:\\)$/i.test(candidatePath);
 }
 
-module.exports = function(options) {
+module.exports = function(options = {}) {
 	let currentPath = defaultValue(options.basePath, __dirname);
 	let checker = defaultValue(options.checker, "package.json");