On the PHP5 unstable branch, I tried the setup wizard with main language Dutch and no additional languages. When finishing the wizard I got a fatal database transaction error and the following error in debug output:

Error: eZMySQLDB

Query error: You have an error in your SQL syntax; check the manual that
corresponds to your MySQL server version for the right syntax to use
near ') AND (lang_mask & 4) > 0' at line 1. Query: UPDATE ezurlalias_ml
SET lang_mask = lang_mask | 1 WHERE action in () AND (lang_mask & 4) > 0

This query is made in eZURLAliasML::setLangMaskAlwaysAvailable().

When choosing another language like English - United Kingdom, it works.
I guess this has something to do with the new language mapping step in
the setup wizard, because I also got an undefined offset 0 warning in
eZContentObjectVersion::unserialize line 1271.

Amos tested this on 3.10 and there it ends up with a fatal error: Call to a member function on a non-object in /home/amos/src/php/ezp310test/kernel/classes/ezcontentobject.php on line 451

Steps to reproduce

I've chosen Dutch as the main language, no additional languages. Left the defaults in the language mapping step.