Handle the case, when a post with no title is displayed in the feed.

It is possible that the title field accidentaly isn't set or intentionaly left empty in the site DB. In that case, we have the following in the feed:


It looks ugly, and we also cannot navigate directly to the post, since the title is the link.

The problem can be solved on the site's side, if the correct SQL query is used. For example:

```
@follow.addFeed("Posts", "
SELECT
post_id AS event_uri,
'post' AS type,
date_published AS date_added,
IFNULL(NULLIF(title, ''), '(untitled)') AS title,
body AS body,
'?Post:' || post_id AS url
FROM post", true)

```

In that example, `IFNULL(NULLIF(title, ''), '(untitled)')` replaces both NULL and the empty string with "(untitled)", so we have in the feed:


But I believe it is better to handle that case on the ZeroHello side. It will be applied to any site, and it also makes possible to localize the '(untitled)' string in a uniform way.

Start by locating the ZeroHello feed rendering and how post titles become links. Check how missing and empty titles are displayed, then make both cases show a localized untitled label while keeping the post navigable; verify the resulting feed behavior for posts without titles.

Vom Indexierungsmodell aus dem Issue-Text verfasst.