Fix a small nit in ping function

Author: meow-developer

promise.js

@@ -161,7 +161,7 @@ class PromiseConnection extends EventEmitter {
     const c = this.connection;
     const localErr = new Error();
     return new this.Promise((resolve, reject) => {
-      c.ping((err) => {
+      c.ping(err => {
         if (err) {
           localErr.message = err.message;
           localErr.code = err.code;