Fix backup/restore of empty DB
Fix backup/restore of empty DB

Do not return errors when performing the backup and the SSO DB is empty.
Conversely, when restoring, don't complain if the SSO DB is not found in the
backup: just clear the current DB.

plotters/accounts-sso.signond,maemo-foss/accounts-sso-signon,plotters/accounts-sso.signond,maemo-foss/accounts-sso-signon,maemo-foss/accounts-sso-signon,plotters/accounts-sso.signond