ui: 修复移动端导航栏丢失的问题

packages/ui-default/components/header/header.page.styl

@@ -91,7 +91,7 @@ $header-gap-mini-domain = ($header-bg-height-mini - $nav-item-height - $header-l
   a, a:visited, a:hover
     color: #FFF
 
-.header--mobile__domain.is--system
+.header--mobile__domain
   display: block
   width: $nav-logo-width    // no rem
   height: $nav-logo-height  // no rem