FIX: only remove custom CSS in admin on first load

app/views/common/_discourse_javascript.html.erb

@@ -9,7 +9,6 @@
 
 <script>
   Ember.RSVP.configure('onerror', function(e) {
-
     // Ignore TransitionAborted exceptions that bubble up
     if (e && e.message === "TransitionAborted") { return; }
 
@@ -43,6 +42,7 @@
   Discourse.Route.mapRoutes();
   Discourse.start();
   Discourse.set('assetVersion','<%= Discourse.assets_digest %>');
+  Discourse.Session.currentProp("disableCustomCSS", <%= loading_admin? %>);
 </script>
 
 <%= script 'browser-update' %>