Fixed about previous exception.

framework/base/HttpException.php

@@ -29,11 +29,12 @@ class HttpException extends UserException
 	 * @param integer $status HTTP status code, such as 404, 500, etc.
 	 * @param string $message error message
 	 * @param integer $code error code
+	 * @param \Exception $previous The previous exception used for the exception chaining.
 	 */
-	public function __construct($status, $message = null, $code = 0)
+	public function __construct($status, $message = null, $code = 0, \Exception $previous = null)
 	{
 		$this->statusCode = $status;
-		parent::__construct($message, $code);
+		parent::__construct($message, $code, $previous);
 	}
 
 	/**