Bug 13169: C4::Templates::themelanguage fails if the DB is not populated

Bug 13169: C4::Templates::themelanguage fails if the DB is not populated

With the aim to remove hardcoded themes the C4::Templates::themelanguage
got dependent on the DB being populated. This patch reintroduced the
hardcoded defaults as a last resort.

To test:
- Do a fresh install, clean your browser's cache, empty DB
- Open the staff interface
=> FAIL: A "Software error" screen shows "Template process failed: file error..."
- Apply the patch
- Reload
=> SUCCESS: The webinstaller prompts for login correctly.
- Sign off :-D

Regards

Signed-off-by: Nick Clemens <nick@quecheelibrary.org>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>