[ticket/12422] Fix debug warning in log search

PHPBB3-12422
[ticket/12422] Add tests

PHPBB3-12422
Merge pull request #2335 from Elsensee/ticket/12422

[ticket/12422] Fix debug warning in log search

* Elsensee/ticket/12422:
  [ticket/12422] Add tests
  [ticket/12422] Fix debug warning in log search