Do not show timeline preview or directory widgets if they are disabled (#10284)

app/views/about/show.html.haml

@@ -17,7 +17,8 @@
         = render 'registration'
 
       .directory
-        .directory__tag{ class: Setting.profile_directory ? nil : 'disabled' }
+        - if Setting.profile_directory
+          .directory__tag
             = optional_link_to Setting.profile_directory, explore_path do
               %h4
                 = fa_icon 'address-book fw'
@@ -28,7 +29,8 @@
                 - @instance_presenter.sample_accounts.each do |account|
                   = image_tag current_account&.user&.setting_auto_play_gif ? account.avatar_original_url : account.avatar_static_url, width: 48, height: 48, alt: '', class: 'account__avatar'
 
-        .directory__tag{ class: Setting.timeline_preview ? nil : 'disabled' }
+        - if Setting.timeline_preview
+          .directory__tag
             = optional_link_to Setting.timeline_preview, public_timeline_path do
               %h4
                 = fa_icon 'globe fw'