Else Statement

Hello
I have this page which will show some catalogs, I would like to have a "else statement" to show a text if no catalogs to find.
I'm not a big fan PHP, so I hope there is someone who can help?

< ?php
/*
Template Name: Catalogue
*/
?>

< ?php get_header(); ?>
< ?php $args = array( 'post_type' => 'catalogue_issuu', 'posts_per_page' => 0);
$loop = new WP_Query( $args );
query_posts('cat=1');
while ($loop->have_posts()) : $loop->the_post();
?>

< ?php endwhile;?>
< ?php get_footer(); ?>