После установки бэкапа на ОС ошибка "Call to a member function get() on null in" - Joomla 3.x: Установка, обновление и настройка

public function get($id, $group, $checkTime = true)
	{
		$cache_id = $this->_getCacheId($id, $group);
		$back = self::$_db->get($cache_id);
		return $back;
	}

$back = self::$_db->get($cache_id);

echo'<pre>';print_r( self::$_db );echo'</pre>'.__FILE__.' '.__LINE__;
die(__FILE__ .' '. __LINE__ );

<?php
/**
 * @package     Joomla.Platform
 * @subpackage  Cache
 *
 * [member=126442]copyright[/member]   Copyright (C) 2005 - 2014 Open Source Matters, Inc. All rights reserved.
 * @license     GNU General Public License version 2 or later; see LICENSE
 */

defined('JPATH_PLATFORM') or die;

/**
 * Memcached cache storage handler
 *
 * @package     Joomla.Platform
 * @subpackage  Cache
 * @see         http://php.net/manual/en/book.memcached.php
 * @since       12.1
 */
class JCacheStorageMemcached extends JCacheStorage
{
	/**
	 * @var    Memcached
	 * @since  12.1
	 */
	protected static $_db = null;

	/**
	 * @var    boolean
	 * @since  12.1
	 */
	protected $_persistent = false;

	/**
	 * @var
	 * @since   12.1
	 */
	protected $_compress = 0;

	/**
	 * Constructor
	 *
	 * @param   array  $options  Optional parameters.
	 *
	 * @since   12.1
	 */
	public function __construct($options = array())
	{
		parent::__construct($options);
		if (self::$_db === null)
		{
			$this->getConnection();
		}
	}

	/**
	 * Return memcached connection object
	 *
	 * @return  object   memcached connection object
	 *
	 * @since   12.1
	 */
	protected function getConnection()
	{
		if ((extension_loaded('memcached') && class_exists('Memcached'))!= true)
		{
			return false;
		}

		$config = JFactory::getConfig();
		$this->_persistent = $config->get('memcache_persist', true);
		$this->_compress = $config->get('memcache_compress', false) == false ? 0 : Memcached::OPT_COMPRESSION;

		/*
		 * This will be an array of loveliness
		 * @todo: multiple servers
		 * $servers	= (isset($params['servers']))? $params['servers'] : array();
		 */
		$server = array();
		$server['host'] = $config->get('memcache_server_host', 'localhost');
		$server['port'] = $config->get('memcache_server_port', 11211);

		// Create the memcache connection
		if ($this->_persistent)
		{
			$session = JFactory::getSession();
			self::$_db = new Memcached($session->getId());
		}
		else
		{
			self::$_db = new Memcached;
		}
		$memcachedtest = self::$_db->addServer($server['host'], $server['port']);

		if ($memcachedtest == false)
		{
			return JError::raiseError(404, "Could not connect to memcached server");
		}

		self::$_db->setOption(Memcached::OPT_COMPRESSION, $this->_compress);

		// Memcached has no list keys, we do our own accounting, initialise key index
		if (self::$_db->get($this->_hash . '-index') === false)
		{
			$empty = array();
			self::$_db->set($this->_hash . '-index', $empty, 0);
		}

		return;
	}

	/**
	 * Get cached data from memcached by id and group
	 *
	 * @param   string   $id         The cache data id
	 * @param   string   $group      The cache data group
	 * @param   boolean  $checkTime  True to verify cache time expiration threshold
	 *
	 * @return  mixed  Boolean false on failure or a cached data string
	 *
	 * @since   12.1
	 */

JRegistry::getvalue()  to JRegistry::get()

ALTER TABLE `#__users` ADD INDEX(`usertype`);