Bug in lib/cleanup.php

I've noticed a bug in the latest Roots with WooCommerce (I'm using version 2.15 but not sure what other versions it affects).

The function roots_request_filter() in lib/cleanup.php affects the dashboard as well and breaks product filtering in WooCommerce.

I've fixed it by adding && !is_admin() to the if statement if (isset($_GET['s']) && empty($_GET['s'])).