core_ACL: Make config/acl.php optional.

git-svn-id: https://simplesamlphp.googlecode.com/svn/trunk@1721 44740490-163a-0410-bde0-09ae8108e29a

modules/core/lib/ACL.php

@@ -56,7 +56,7 @@ class sspmod_core_ACL {
 	private static function getById($id) {
 		assert('is_string($id)');
 
-		$config = SimpleSAML_Configuration::getConfig('acl.php');
+		$config = SimpleSAML_Configuration::getOptionalConfig('acl.php');
 		if (!$config->hasValue($id)) {
 			throw new SimpleSAML_Error_Exception('No ACL with id ' . var_export($id, TRUE) . ' in config/acl.php.');
 		}