Fix usage of non-existant property.

Use the declared `_result` property instead. I would normally add
a test, but getting to this path requires a query to fail which is not
simple to simulate in the test harness.

Fixes #11615

lib/Cake/Model/Datasource/DboSource.php

@@ -470,7 +470,7 @@ protected function _execute($sql, $params = array(), $prepareOptions = array())
 			$query = $this->_connection->prepare($sql, $prepareOptions);
 			$query->setFetchMode(PDO::FETCH_LAZY);
 			if (!$query->execute($params)) {
-				$this->_results = $query;
+				$this->_result = $query;
 				$query->closeCursor();
 				return false;
 			}