mod_rewrite condition for existing folder
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I'm trying to set-up an *.htaccess* file that will pass every request URL as `GET` into a file called `index.php`. The only exception is, when the request URL points to a directory *res*.

Examples:

    /wiki/cool-stuff          => index.php?uri=/wiki/cool-stuff
    /wiki/cool-stuff?news=on  => index.php?uri=/wiki/cool-stuff&news=on
    /res/cool-photo.jpg       => res/cool-photo.jpg

Two problems:

 1. The GET variable passed to `/wiki/cool-stuff` in the second example is not passed to *index.php*
 2. Accessing `/res` (not `/res/`!!) suddenly shows me `/res/?uri=res` **in my browser** and *index.php* with `uri=res/`. Accessing `/res/` instead, shows me *index.php* with `uri=res/` and the URL in the browser stays (which is okay).

The *.htaccess*:

    RewriteEngine on
    RewriteBase   /subthing/

    RewriteCond   %{REQUEST_URI}    !/res/(.+)$
    RewriteCond   %{REQUEST_URI}    !index.php
    RewriteRule   (.*)              index.php?uri=$1 


How can I achieve the desired behaviour?