FacebookAuthProvider: sanitize locale
FacebookAuthProvider: sanitize locale

Fixes: 7ac4a7e6b135 ("GoogleAuthProvider: FacebookAuthProvider: extract users locale")
Signed-off-by: Jan Viktorin <3eab6ac54c005c4408f608556a6663b7f2abede7@fit.vutbr.cz>

BeeeOn/server,BeeeOn/server,BeeeOn/server,BeeeOn/server