Migration from Nuxeo 5.4 to 5.5.0 creates inconsistant ancestors table on Oracle

When upgrading from 5.4.x to 5.5 the ancestors table is populated using the nx_init_ancestors function.
This function add an empty ancestor collection for the Root element and it may raise error like:

Exception: java.sql.SQLException. message: ORA-06502: PL/SQL: numeric or value error ORA-06512: at "NUXEO.NX_ANCESTORS", line 10