format fixed, substr changed to mb_substr, database-related settings added

framework/console/controllers/MessageController.php

@@ -182,7 +182,7 @@ class MessageController extends Controller
 
 		if (!$removeUnused) {
 			foreach ($obsoleted as $pk => $m) {
-				if (substr($m, 0, 2) === '@@' && substr($m, -2) === '@@') {
+				if (mb_substr($m, 0, 2) === '@@' && mb_substr($m, -2) === '@@') {
 					unset($obsoleted[$pk]);
 				}
 			}