DEV: Fix build

Follow-up to bd3c0dd59f.

app/controllers/application_controller.rb

@@ -785,7 +785,9 @@ class ApplicationController < ActionController::Base
       opts[:layout] = 'application' if opts[:layout] == 'no_ember'
     end
 
-    if !SiteSetting.login_required? || (current_user rescue false)
+    @current_user = current_user rescue nil
+
+    if !SiteSetting.login_required? || @current_user
       key = "page_not_found_topics"
       if @topics_partial = Discourse.redis.get(key)
         @topics_partial = @topics_partial.html_safe

app/views/exceptions/not_found.html.erb

@@ -1,7 +1,7 @@
 <div class="page-not-found">
   <h1 class="title"><%= @title %></h1>
 
-  <%- if !current_user %>
+  <%- if !@current_user %>
     <a href="<%= path "/login" %>" class='btn btn-primary'><%= SvgSprite.raw_svg('fa-user') %><%= I18n.t('log_in') %></a>
   <%- end %>