Improvements for 30871:

Improvements for 30871:
* Use !empty() to avoid notices if $s->page_is_redirect isn't set.
* Enable unconditionally.  This causes some extra queries, but only if
makeLinkObj() is being used, which for typical article links it's not.
(The previous version didn't add page_is_redirect to the parameter even
when it would have caused no extra queries, in two places in
Parser.php.)  If the extra makeLinkObj() queries are a problem, they can
be combined with the existence check query.  Or failing that, it can
just be reverted for that method only, which will still allow the
feature to work with standard in-article links.