make sure that the crypt library is loaded

apps/files_encryption/files/error.php

@@ -2,6 +2,7 @@
 
 if (!isset($_)) { //also provide standalone error page
 	require_once __DIR__ . '/../../../lib/base.php';
+	require_once __DIR__ . '/../lib/crypt.php';
 
 	$l = OC_L10N::get('files_encryption');