[BUGFIX] Nginx if directory should have "" instead of ()

[ramonfincken]

[BUGFIX] Nginx if directory should have "" instead of ()

if not changed nginx -t fails on
nginx: [emerg] invalid condition "$http_user_agent" in ..

[pothi]

Hello,

Thanks for the bug report and pull request. It could happen when a new "user agent" string is added to the list without escaping special characters (such as space) with a backslash. We can't expect the user to escape the "user agent" string in advance. So, changing braces to quotes (single or double) is more compatible and more user-friendly.

Thanks again,
Pothi.