WP 2.9.2 – feed error – blank feed with filter

Hi, guys.

My feed is empty after the update to 2.9.2.

I use a small plugin to filter my feed to include just one category.

the code is the following:

<?php
/*
Plugin Name: Feed Filter
Plugin URI:
Description: Filters your feed to include only certain categories.
Version: 0.1
Author: Daniel Trezub
Author URI: http://www.gameblogs.com.br

*/
add_filter('pre_get_posts','filterRSSQuery');
function filterRSSQuery($query) {
	if ($query->is_feed) {
        $query->set('cat','49');
    }
return $query;
}
?>

If I disable this little plugin, the feed works ok, but with all categories, of course.

If I enable it, the feeds does not validate and shows empty (saying something like “Error parsing XML: no element found”.

In the feedvalidator.org website it returns me “line 1, column 0: XML parsing error: <unknown>:1:0: no element found”

Note that before the update to 2.9.2. everything was working great. No changes were made to ANY file on the installation.

I’ve already tried to use $query->set('category_name','GameBlogs'); with the same results.

Any ideas, please?