fix: fatal error if no middleware in route

middleware  was declared without initialize. If there no middleware was
used in route it triggers fatal error in merge as this one is not array.

Author: abdul-kaioum

src/Http/Router/RouteBase.php

@@ -43,7 +43,7 @@ final class RouteBase
 
     private $_ignoreToken;
 
-    private $_middleware;
+    private $_middleware = [];
 
     private static $_isGrouped;