block("lightgreen", "added session");
   }
 
-  if($_GET['delete']!="") {
+  if(isset($_GET['delete'])) {
     $db->query("DELETE FROM sessions WHERE id=" . $_GET['delete']);
     block("red", "deleted session");
   }
 </form>
 
 <?php
+  if ( $SESSIONS_n == 0 ) {
+    block("red", "no sessions defined");
+    exit;
+  }
+
   block("black", "session overview");
 
   print "<table>";