workaround issue where orphan user_avatar record exists

app/jobs/scheduled/create_missing_avatars.rb

@@ -5,6 +5,7 @@ module Jobs
     def execute(args)
       # backfill in batches of 5000 an hour
       UserAvatar.includes(:user)
+                .joins(:user)
                 .where(last_gravatar_download_attempt: nil)
                 .order("users.last_posted_at DESC")
                 .limit(5000)