Fixed an issue where the first parameter in a callback would not be the

expected error object.

lib/prompt.js

@@ -689,7 +689,7 @@ prompt.addProperties = function (obj, properties, callback) {
   });
 
   if (properties.length === 0) {
-    return callback(obj);
+    return callback(null, obj);
   }
 
   prompt.get(properties, function (err, results) {