fix(admin): unify settings save controls

src/Admin/GlobalController.php

@@ -173,6 +173,9 @@ class GlobalController extends ControllerBase {
             'enabled'           => !empty($params['enabled']),
             'scroll_hide'       => !empty($params['scroll_hide']),
             'scroll_down_hide'  => !empty($params['scroll_down_hide']),
+            'footer_tabbar_single' => in_array($params['footer_tabbar_single'] ?? '', ['default', 'extend'], true)
+                ? $params['footer_tabbar_single']
+                : 'default',
             'max_items'         => $max_items,
             'icon_size'         => max(16, min(32, (int) ($params['icon_size'] ?? 22))),
             'text_size'         => max(8, min(14, (int) ($params['text_size'] ?? 10))),