fix check for error argument

lib/index.js

@@ -60,7 +60,7 @@ exports.publish = function publish(basePath, config, callback) {
   var done = function(arguments) {
     try {
       (callback || function(err) {
-        if (!err) {
+        if (!!err) {
           console.log(err)
         }
       })(arguments);