Looking at the code at line 58// clean out site caches
$cache = JCache::getInstance('', $options);
$site_caches = array_keys($cache->getAll());
...this looks to be related to the code trying to clean caches.
Have your tried to clear cache from the admin interface?
Maybe a directory was deleted?
Any error from the joomla system information pages?
Is this appearing on the public facing side or just admin?