Improper handling of unset

[adespawn]

Somehow, this missed also my review.
https://github.com/scylladb-zpp-2024-javascript-driver/scylladb-javascript-driver/blob/1f87b2f26d42650f32b84fe5e83c452579520884/lib/types/cql-utils.js#L323-L334

Fix this and maybe add regression tests for that

[adespawn]

Added some logic for fixing it in #236, but this can be improved to reduce code duplication