When IP geolocation returned no matching CIDR block, LookupCountryByIP returned an empty string with nil error. The handler took the address of that empty string, producing a non-nil pointer to "", which was inserted into the database. Guard against this by returning nil when the resolved country code is empty, and backfill existing rows with a migration. Signed-off-by: Émile Ré <emile@getprobo.com>