Pagination not working with pagenavi

I added the following to my functions.php file and it worked:

function toolset_fix_custom_posts_per_page( $query_string ){
if( is_admin() || ! is_array( $query_string ) )
    return $query_string;

$post_types_to_fix = array(
    array(
        'post_type' => 'news_article',
        'posts_per_page' => 6
    ),
    // add another if you want
    /*
    array(
        'post_type' => 'movie',
        'posts_per_page' => 2
    ),
    */
);

foreach( $post_types_to_fix as $fix ) {
    if( array_key_exists( 'post_type', $query_string )
        && $query_string['post_type'] == $fix['post_type']
    ) {
        $query_string['posts_per_page'] = $fix['posts_per_page'];
        return $query_string;
    }
}

return $query_string;

}

add_filter( ‘request’, ‘toolset_fix_custom_posts_per_page’ );