message: Be defensive about user RSS updated at
diff: @@ -23,7 +23,7 @@ const UserRss: React.FC<UserRssProps> = ({ params }) => {
  title={`Are.na / ${user.name}`}
  link={user.href}
  atomLink={`${user.href}/feed/rss`}
  - lastBuildDate={user.contents[0].updated_at}
  + lastBuildDate={user.contents[0]?.updated_at}
  >
  {user.contents.map(block => {
  return <RssBlock key={block.id} block={block} />
  