/**
	 * Constructor: builds array of $changeItems by processing the .sql files in a folder.
	 * The folder for the Joomla core updates is `administrator/components/com_admin/sql/updates/<database>`.
	 *
	 * @param   \JDatabaseDriver  $db      The current database object
	 * @param   string            $folder  The full path to the folder containing the update queries
	 *
	 * @since   2.5
	 */
	public function __construct($db, $folder = null)
	{
		$this->db = $db;
		$this->folder = $folder;
		$updateFiles = $this->getUpdateFiles();
		$updateQueries = $this->getUpdateQueries($updateFiles);

		foreach ($updateQueries as $obj)
		{
			$changeItem = ChangeItem::getInstance($db, $obj->file, $obj->updateQuery);

			if ($changeItem->queryType === 'UTF8CNV')
			{