Error on r2871 Install

Fatal error: Call to a member function install() on a non-object in /Users/markkaplan/Sites/modx_testing/097_8_6_07/setup/includes/modinstall.class.php on line 468

        if ($this->xpdo) {
            // add required core data
            $this->xpdo->loadClass('transport.xPDOTransport', XPDO_CORE_PATH, true, true);
            
            $this->xpdo->setPackage('modx', MODX_CORE_PATH . 'model/');

            $packageDirectory= MODX_CORE_PATH . 'packages/';
            $packageState= $this->config['unpacked'] == 1 ? XPDO_TRANSPORT_STATE_UNPACKED : XPDO_TRANSPORT_STATE_PACKED;
            $package= xPDOTransport :: retrieve($this->xpdo, $packageDirectory . 'core.transport.zip', $packageDirectory, $packageState);
            
            if (!defined('MODX_BASE_PATH')) define('MODX_BASE_PATH', $this->config['web_path']);
            if (!defined('MODX_ASSETS_PATH')) define('MODX_ASSETS_PATH', $this->config['assets_path']);
            if (!defined('MODX_MANAGER_PATH')) define('MODX_MANAGER_PATH', $this->config['mgr_path']);
            if (!defined('MODX_CONNECTORS_PATH')) define('MODX_CONNECTORS_PATH', $this->config['connectors_path']);
            
            $package->install(array (
                XPDO_TRANSPORT_PRESERVE_KEYS => true, 
                XPDO_TRANSPORT_RESOLVE_FILES => ($this->config['inplace'] == 0 ? 1 : 0)
            ));