[Plugin: Members List Plugin] Empty page for user without any post

Hi!
I have this problem in this test forum (it not contain banner and is work in progress, please do not consider a spam post).
–
http://www.orgogliopeloritano.it/lista-utenti/
If you click on “Noschese” you can see a valid author page.
If you click on “testuser” (an user without any post) you can’t see gravatar and description.
I think is a problem with loop.php:

<?php /* If there are no posts to display, such as an empty archive page */ ?>
<?php if ( ! have_posts() ) : ?>
	<div id="post-0" class="post error404 not-found">
		<h1 class="entry-title"><?php _e( 'Nessun risultato trovato', 'twentyten' ); ?></h1>
		<div class="entry-content">
			<p><?php _e( 'Spiacente, nessun risultato &egrave; stato trovato per il suddetto archivio.<br />Forse una ricerca potr&agrave; aiutarti a trovare il post/l\'articolo desiderato.', 'twentyten' ); ?></p>
			<?php get_search_form(); ?>
		</div><!-- .entry-content -->
	</div><!-- #post-0 -->
<?php endif; ?>

Edit: i’ve see also that user_nicename show the slug and not the real nicename.
How i can fix? :/

http://wordpress.org/extend/plugins/members-list/