Tread unreadable countries as "unknown"

vino.go

@@ -55,7 +55,8 @@ func (i *ISO2CountryCode) UnmarshalBinary(d []byte) error {
 	}
 
 	if len(d) != 2 {
-		return errors.New("invalid length")
+		*i = UnknownCountry
+		return nil
 	}
 
 	*i = ISO2CountryCode{d[0], d[1]}