stream: fix eventNames() to not return not defined events

Author: ilyasShabiCS

lib/events.js

@@ -888,7 +888,11 @@ function listenerCount(type, listener) {
  * @returns {any[]}
  */
 EventEmitter.prototype.eventNames = function eventNames() {
-  return this._eventsCount > 0 ? ReflectOwnKeys(this._events) : [];
+  const names = [];
+  for (const key of ReflectOwnKeys(this._events))
+    this._events[key] !== undefined && names.push(key);
+
+  return names;
 };
 
 function arrayClone(arr) {