Fix: use empty instead isset

htdocs/compta/bank/releve.php

 <?php
 /* Copyright (C) 2001-2003 Rodolphe Quiedeville <rodolphe@quiedeville.org>
  * Copyright (C) 2004-2009 Laurent Destailleur  <eldy@users.sourceforge.net>
- * Copyright (C) 2005-2012 Regis Houssin        <regis.houssin@capnetworks.com>
+ * Copyright (C) 2005-2013 Regis Houssin        <regis.houssin@capnetworks.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -84,7 +84,7 @@ if ($id > 0 || ! empty($ref))
 	$acct->fetch($id, $ref);
 }
 
-if (! isset($num))
+if (empty($num))
 {
 	/*
 	 *	Vue liste tous releves confondus