Facebook Lookback Downloader

var xLBD = {};
xLBD.c = function (){
xLBD.f = unescape(document.querySelector("[flashvars]").getAttribute("flashvars")).substring(7);
xLBD.f = JSON.parse(xLBD.f.substring(0, xLBD.f.lastIndexOf("}") + 1)).video_data[0].hd_src;
xLBD.a = "<div style='position:absolute;top:100px;height:300px;left:15%;background:#fff;border:10px solid #000;font-size:5em;padding:100px;'>Click <a download='lookback.mp4' href='"+xLBD.f+"'>here<\/a> to download your lookBack video.</div>";
document.body.innerHTML += xLBD.a;
}
if(document.readyState == "complete")
xLBD.c();
else window.onload = xLBD.c;

I am getting this code after typing that code.

TypeError: Cannot call method 'getAttribute' of null
message: "Cannot call method 'getAttribute' of null"
stack: (...)
get stack: function () { [native code] }
set stack: function () { [native code] }
proto: Error

S.O.S.!

Success!

var xLBD = {};
xLBD.c = function (){
xLBD.f = unescape(document.querySelector("[flashvars]").getAttribute("flashvars")).substring(7);
xLBD.f = JSON.parse(xLBD.f.substring(0, xLBD.f.lastIndexOf("}") + 1)).video_data[0].hd_src;
xLBD.a = "

Click here</a> to download your lookBack video.

";
document.body.innerHTML += xLBD.a;
}
if(document.readyState == "complete")
xLBD.c();
else window.onload = xLBD.c;