fix undefined check

index.js

@@ -20,7 +20,7 @@ Challenge.create = function (options) {
   results.create = undefined;
 
   Object.keys(defaults).forEach(function (key) {
-    if ('undefined' !== typeof options[key]) {
+    if ('undefined' === typeof options[key]) {
       options[key] = defaults[key];
     }
   });