ui: 修复移动端导航栏丢失的问题

packages/ui-default/templates/extra.css

@@ -6,7 +6,7 @@
 
 @media only screen and (-webkit-min-device-pixel-ratio: 1.5), only screen and (min-resolution: 1.5dppx), only screen and (min-resolution: 144dpi) {
     /* {% if nav_logo_dark_2x %} */
-    .nav__logo, .header--mobile__domain.is--system {
+    .nav__logo, .header--mobile__domain {
         background-image: url({{nav_logo_dark_2x}}) !important
     }
     /* {% endif %} */

packages/ui-default/templates/partials/header_mobile.html

@@ -1,12 +1,10 @@
-{% if no_path_section %}
 <div class="header--mobile">
   <div class="row"><div class="columns clearfix">
     <div class="float-left">
-      <a class="header--mobile__domain is--system" href="/" target="_self">&nbsp;</a>
+      <a class="header--mobile__domain" href="/" target="_self">&nbsp;</a>
     </div>
     <div class="float-right">
       {% include "partials/hamburger.html" %}
     </div>
   </div></div>
 </div>
-{% endif %}