Category Table and Data with foreign key on root plus exception got

exception.txt

'PDOException' with message 'SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails (`gandaancestry`.`category`, CONSTRAINT `fk_category_root` FOREIGN KEY (`root`) REFERENCES `category` (`id`) ON DELETE SET NULL ON UPDATE SET NULL)' in D:\Program Files\Apache Group\Apache\htdocs\gandaancestry\library\Doctrine\DBAL\Statement.php:131 Stack trace: #0 D:\Program Files\Apache Group\Apache\htdocs\gandaancestry\library\Doctrine\DBAL\Statement.php(131): PDOStatement->execute(NULL) #1 D:\Program Files\Apache Group\Apache\htdocs\gandaancestry\library\Doctrine\ORM\Persisters\BasicEntityPersister.php(239): Doctrine\DBAL\Statement->execute() #2 D:\Program Files\Apache Group\Apache\htdocs\gandaancestry\library\Doctrine\ORM\UnitOfWork.php(896): Doctrine\ORM\Persisters\BasicEntityPersister->executeInserts() #3 D:\Program Files\Apache Group\Apache\htdocs\gandaancestry\library\Doctrine\ORM\UnitOfWork.php(304): Doctrine\ORM\UnitOfWork->executeInserts(Object(Doctrine\ORM\Mapping\ClassMetadata)) #4 D:\Program Files\Apache Group\Apache\htdocs\gandaancestry\library\Doctrine\ORM\EntityManager.php(355): Doctrine\ORM\UnitOfWork->commit(NULL) #5 D:\Program Files\Apache Group\Apache\htdocs\gandaancestry\application\views\scripts\index\index.phtml(40): Doctrine\ORM\EntityManager->flush()

modelanddata.sql

-- phpMyAdmin SQL Dump
-- version 3.3.9
-- http://www.phpmyadmin.net
--
-- Host: localhost
-- Generation Time: May 23, 2012 at 03:38 PM
-- Server version: 5.1.41
-- PHP Version: 5.3.5

SET SQL_MODE="NO_AUTO_VALUE_ON_ZERO";

--
-- Database: `gandaancestry`
--

-- --------------------------------------------------------

--
-- Table structure for table `category`
--

DROP TABLE IF EXISTS `category`;
CREATE TABLE `category` (
  `id` int(11) unsigned NOT NULL AUTO_INCREMENT,
  `title` varchar(64) NOT NULL,
  `lvl` int(11) unsigned DEFAULT NULL,
  `lft` int(11) unsigned DEFAULT NULL,
  `rgt` int(11) unsigned DEFAULT NULL,
  `root` int(11) unsigned DEFAULT NULL,
  `parent_id` int(11) unsigned DEFAULT NULL,
  PRIMARY KEY (`id`),
  KEY `fk_category_parent` (`parent_id`),
  KEY `fk_category_root` (`root`),
  CONSTRAINT `fk_category_root` FOREIGN KEY (`root`) REFERENCES `category` (`id`) ON DELETE SET NULL ON UPDATE SET NULL,
  CONSTRAINT `fk_category_parent` FOREIGN KEY (`parent_id`) REFERENCES `category` (`id`) ON DELETE SET NULL ON UPDATE SET NULL
) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8;

--
-- Dumping data for table `category`
--

INSERT INTO `category` (`id`, `title`, `lvl`, `lft`, `rgt`, `root`, `parent_id`) VALUES
(6, 'Food', 0, 1, 8, 6, NULL),
(7, 'Fruits', 1, 2, 3, 6, 6),
(8, 'Vegetables', 1, 4, 7, 6, 6),
(9, 'Carrots', 2, 5, 6, 6, 8);