adding default to $hint within ctor of DatabaseSetupException

lib/setup.php

@@ -4,7 +4,7 @@ class DatabaseSetupException extends Exception
 {
 	private $hint;
 
-	public function __construct($message, $hint, $code = 0, Exception $previous = null) {
+	public function __construct($message, $hint = '', $code = 0, Exception $previous = null) {
 		$this->hint = $hint;
 		parent::__construct($message, $code, $previous);
 	}