It happens when an extension has just been live-deployed into the running
soffice process and then trying to instantiate out-of-process in an additional
uno process one of that extension's shared library components and that component
---erroneously---uses the "prefix" feature.  (Which can be reproduced with the
mysql-connector-ooo.oxt extension, --enable-ext-mariadb-connector: "rm -rf
instdir/*/share/extensions/mysql-connector-ooo", "instdir/*/program/soffice
workdir/*/Extension/mysql-connector.oxt", install the per-user, then "File - New
- Database - Connect to an existing database: MySQL - Next >> - Connect directly
- Next >> - Database name: foo - Server / Port - Server: bar - Next >> - Test
Connection", crash.)

Change-Id: Ibab2ad31199eec5dc26ffa337a5e3e7490f782d7