web log issue

I started noticing this in my server logs a while ago. Please help!

Code:

[B]ispconfig/scripts/shell/logs.php

PHP Warning:  Invalid argument supplied for foreach() in /root/ispconfig/scripts/shell/logs.php on line 173[/B]

[COLOR=Red][B][I]__line 173__[/I][/B][/COLOR]
foreach($index as $i => $t) {
    if($t < time()-86400*$purge) {
      @unlink($dir.'/'.$files[$i]);
    }
  }
}

$time_end = getmicrotime();
$dauer = $time_end - $time_start;
//echo "Duration: $dauer seconds. Lines: $zeilen_gesamt\n";

?>

====================================================================

[B]PHP Warning:  readlink(): Invalid argument in /root/ispconfig/scripts/shell/logs.php on line 125
[/B]

// Traffic auswerten und Symlinks für Webalizer aktualisieren
foreach($traffic as $virtual_host => $bytes) {

        if(trim($virtual_host) != '' && trim($virtual_host)!='localhost') {
                // Traffic in DB Schreiben
                // Bestimme Web-ID
[COLOR=Red][I][B] __line 125___ [/B][/I][/COLOR]      $link =  readlink("$webroot/$virtual_host");
                $parts = split("/",$link);
                $web_id = intval(substr($parts[count($parts) - 1],3));