`lib::CmdResult::code()` called `Option::unwrap()` on a `None` value

[xtqqczze]

---- test_dd::test_random_73k_test_count_bytes stdout ----
bin: "/target/x86_64-unknown-linux-musl/debug/coreutils"
run: /target/x86_64-unknown-linux-musl/debug/coreutils dd ibs=521 obs=1031 count=32x1024 iflag=count_bytes if=random-5828891cb1230748e146f34223bbd3b5.test

thread 'test_dd::test_random_73k_test_count_bytes' panicked at tests/uutests/src/lib/util.rs:412:35:
called `Option::unwrap()` on a `None` value

https://github.com/uutils/coreutils/actions/runs/21295271871/job/61299669959?pr=10454#step:15:5230