optimization: prefer relation.none over relation.where("false")

Using `relation.none` instead of `relation.where("false")` avoids an sql query.

app/models/post_archive.rb

@@ -22,7 +22,7 @@ class PostArchive < ApplicationRecord
       if user_id
         where("updater_id = ?", user_id)
       else
-        where("false")
+        none
       end
     end