Allow uploads:missing Rake task to be run for a single site.

lib/tasks/uploads.rake

@@ -318,16 +318,22 @@ end
 
 # list all missing uploads and optimized images
 task "uploads:missing" => :environment do
-
-  public_directory = "#{Rails.root}/public"
-
+  if ENV["RAILS_DB"]
+    list_missing_uploads
+  else
     RailsMultisite::ConnectionManagement.each_connection do |db|
+      list_missing_uploads
+    end
+  end
+end
 
+def list_missing_uploads
   if Discourse.store.external?
     puts "This task only works for internal storages."
-      next
+    return
   end
 
+  public_directory = "#{Rails.root}/public"
 
   Upload.find_each do |upload|
 
@@ -359,9 +365,6 @@ task "uploads:missing" => :environment do
     end
     puts path if bad
   end
-
-  end
-
 end
 
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