Random button generator needs fixing. Any help would be very much appreciated : My web page:

-http://www.theeventlister.com/landingpage/events/uk/boardmasters.html

Okay so on this website, I have a random button generator, named 'next event'. The button is okay however needs an improvement. Sometimes this button loads the same page the user is on multiple times, I'm not sure how to edit this, this is my code. 

my code:

    var sites = [
        'http://www.theeventlister.com/landingpage/events/uk/boardmasters.html',
        'http://www.theeventlister.com/landingpage/events/uk/reading.html',
        'http://www.theeventlister.com/landingpage/events/uk/rizefest.html',
        'http://www.theeventlister.com/landingpage/events/uk/bestival.html',
        'http://www.theeventlister.com/landingpage/events/uk/creamfields.html',
        'http://www.theeventlister.com/landingpage/events/uk/feastival.html',
        'http://www.theeventlister.com/landingpage/events/uk/fusion.html',
        
        
    ];

    function randomSite() {
        var i = parseInt(Math.random() * sites.length);
        location.href = sites[i];
    }

Thank you!

