Weird RabbitMQ admin webpage behavior with ReferenceError: queue_length is not defined messages.

When you upgrade your RabbitMQ from 3.0.x to 3.1.5 or something, you might see following error on RabbitMQ admin webpage, and admin function doesn't work properly.

ReferenceError: queue_length is not defined

 One and only thing you just need to do in this case is, "Clean your web browser cache", especially cookie.
Once you remove those and reload page, RabbitMQ will require admin/password again. Do log in, you'll see problem has solved.