Fix potential XSS when attacker takes control over http://at.hackerspace.pl/api

js/checkinator-header.js

@@ -1,7 +1,7 @@
 jQuery(document).ready(function() {
     function checkinify() {
          jQuery.getJSON("http://at.hackerspace.pl/api", function(data) {
-          var users = data.users.length;
+          var users = parseInt(data.users.length) || 0;
           var tooltip = jQuery('#status-tooltip');
           var text = 'According to <a href="http://at.hackerspace.pl">our instruments</a> there ';
           if (users == 1)