Merge branch 'master' into glitch-soc/merge-upstream

Conflicts:
- app/models/form/admin_settings.rb
- config/locales/ja.yml

app/models/form/admin_settings.rb

@@ -28,6 +28,9 @@ class Form::AdminSettings
     profile_directory
     hide_followers_count
     flavour_and_skin
+    thumbnail
+    hero
+    mascot
   ).freeze
 
   BOOLEAN_KEYS = %i(
@@ -73,7 +76,7 @@ class Form::AdminSettings
       next if PSEUDO_KEYS.include?(key)
       value = instance_variable_get("@#{key}")
 
-      if UPLOAD_KEYS.include?(key)
+      if UPLOAD_KEYS.include?(key) && !value.nil?
         upload = SiteUpload.where(var: key).first_or_initialize(var: key)
         upload.update(file: value)
       else