allow all characters except forward slash as file extension

src/Control/Controller.php

@@ -696,7 +696,7 @@ public static function join_links($arg = null)
         // add trailing slash if enabled and url does not contain a file extension
         if (static::config()->get('add_trailing_slash') === true
             && substr($result, -1) !== '/'
-            && !preg_match('/^(.*)\.([A-Za-z][A-Za-z0-9]*)$/', $result)
+            && !preg_match('/^(.*)\.([^\/]*)$/', $result)
         ) {
             $result = rtrim($result, '/') . '/';
         }