Whenever the theme updates via Millenium, custom.css is replaced, deleting user customizations

[cheatfreak47]

Whenever Millenium downloads and sets up an update for the theme with it's updates screen, the custom.css file is replaced outright, deleting any customization that the user might have done.

I don't know what a good solution is for this problem, but it definitely is an issue. Ideally the customization loaded in the css file should be applied via a theme settings menu anyway- but I have no idea how viable that is.

Either way, reporting it in case it's a problem that isn't known about.