optimization of tree behavior as per ticket #2600

lib/Cake/Model/Behavior/TreeBehavior.php

@@ -117,8 +117,9 @@ class TreeBehavior extends ModelBehavior {
  */
 	public function beforeDelete($Model, $cascade = true) {
 		extract($this->settings[$Model->alias]);
-		list($name, $data) = array($Model->alias, $Model->read());
-		$data = $data[$name];
+		$data = current($Model->find('first', array(
+			'conditions' => array($Model->alias . '.' . $Model->primaryKey => $Model->id), 
+			'fields' => array($Model->alias . '.' . $left, $Model->alias . '.' . $right))));
 
 		if (!$data[$right] || !$data[$left]) {
 			return true;