[BUG] Index in array not defined

[enumag]

https://github.com/nightsh/kcfinder/blob/6f90cc65e893d421bc94675c364467e78ee4d5df/core/browser.php#L138 is wrong, $_COOKIE['username'] may not be defined and then KCFinder won't load at all (depends on error_reporting, I use strictly E_ALL on localhost).

[nightsh]

I'll try to migrate away from cookies, they are faulty and I really hope to find another way, maybe use HTTP requests only. The main idea is I want to implement some kind of user isolation, so we can have separate users on separate subtrees in /uploads. I'm dealing right now with the authentication problem, and had close to no time to solve this, thus leading to some unstable code in master. I'll have a nice and free period during holidays, so I'll get to fix that around Xmas :-)
Thank you for reporting this, and for your interest in KCFinder!