FarmConfigLoader should display 404 on nonexistent URLs

[hexmode]

The 404 handler can end up with a white page. It wasn't until I enabled display of exceptions that I saw:


Fatal error: Uncaught Exception: Error: staging.icannwiki.org/Special:Version does not exist in urlToWikiIdMap. in /var/www/mediawiki/w/FarmConfigLoader.php:109
Stack trace:
#0 /var/www/mediawiki/w/CanastaDefaultSettings.php(97): require_once()
#1 /var/www/mediawiki/w/LocalSettings.php(8): require_once('...')
#2 /var/www/mediawiki/w/includes/Setup.php(218): require_once('...')
#3 /var/www/mediawiki/w/includes/WebStart.php(86): require_once('...')
#4 /var/www/mediawiki/w/index.php(44): require('...')
#5 {main}
thrown in /var/www/mediawiki/w/FarmConfigLoader.php on line 109