Bug and solution: PHP Notice on Gallery upload

I was getting a PHP Notice because an array key 'Content-Length' was not found in media/mint/js/mooupload/mooupload.php [84].

While debugging it, I saw that 'X-File-Size' was being set instead, so I changed that line to:

    $response ['size'] = isset($headers ['Content-Length']) ? $headers ['Content-Length'] : $headers ['X-File-Size'];

Notices are gone...