If you have a LocalSettings.php in place, but an empty database, going to index.php results in an error. If you go to /mw-config you go through the installation wizard, but then are prompted to download the updated LocalSettings.php again.

I think this should be updated in this way:

1. If a LocalSettings.php file exists and a database connection can be made, but the database is empty, the user should be prompted to install MediaWiki. The install wizard should only ask you questions whose answers do not need to modify LocalSettings.php (i.e. it should ask for the admin user/password, but not the wiki name).
2. If a LocalSettings.php file exists but a database connection cannot be made, then the install wizard should proceed as normal, but should append any needed changes to the end of the existing LocalSettings.php before asking the user to download the updated file.

The only alternative I can think of is for the web server to update the file, but since we don't do that already, it's probably a bad time to start.