Standard value for benchmarks/structures/option_fail.rs not failing

The difference between `option_fail.rs` and `option.rs` lies in the assumption that y > 0, yet the standard value for y is set as `2u64` so the assertion is not failing in `option_fail`.

Is there an error in that the y standard value is supposed to be `0u64` so that the `verifier::unreachable!` macro is called or am I missing another scenario where it is supposed to fail?