A language with a better type system, such as Rust or C++ (which has std::optional) can help prevent this kind of error.
Oh, come on. C++ didn’t get std::optional until C++17. I understand the writer is trying to say “we could have avoided this!”, but even Rust (which does have an Optional<T> type) probably didn’t exist in its current form until maybe two years ago.
That said, this is not about programming languages.