Looks like it's to catch the case where you've got music playing and inadvertently close the tab. There should probably be a check to make sure you've actually got something playing in your queue.
We do that when you have music playing and we also currently do it in the first 30 seconds of loading the page as an awful hack around some completely crappy ads that force redirects that have gotten into our ad networks. It's just in there until we can get the ad problem fixed.
