Cannot redefine property: fullscreenElement

[JobaDiniz]

Hi, I'm guessing this condition is wrong (taken from here):

if (!document.fullscreenElement) {
    Object.defineProperty(document, 'fullscreenElement', {
      get: function() {
        return document.mozFullScreenElement ||
               document.msFullscreenElement ||
               document.webkitFullscreenElement;
      }
    });
  }

[joeyparrish]

Already fixed in master by 7ea820c, but we'll leave this open until we've released v1.3.1, which will contain a cherry-pick of this fix. Thanks!