[ticket/12381] Fix broken error message when selecting invalid DB driver

PHPBB3-12381
Merge pull request #2279 from Elsensee/ticket/12381

[ticket/12381] Fix broken error message when selecting invalid DB driver

* Elsensee/ticket/12381:
  [ticket/12381] Fix broken error message when selecting invalid DB driver
Merge branch 'develop-olympus' into develop-ascraeus

* develop-olympus:
  [ticket/12381] Fix broken error message when selecting invalid DB driver