Revert "[minor] Remove unneeded if statement"

This reverts commit 297f56d.

Author: lpinca

lib/websocket.js

@@ -901,6 +901,8 @@ function socketOnError() {
   this.removeListener('error', socketOnError);
   this.on('error', NOOP);
 
-  websocket.readyState = WebSocket.CLOSING;
-  this.destroy();
+  if (websocket) {
+    websocket.readyState = WebSocket.CLOSING;
+    this.destroy();
+  }
 }