What is the ruling if a conditional divorce decree ('You are divorced if Zayd arrives') is issued, and Zayd arrives while the wife is menstruating?

Primary text

If a man states, 'You are divorced if Zayd arrives,' and Zayd arrives while she is menstruating, the divorce occurs according to the Sunnah of bad practice (Talaq lil-bid'ah), but the husband incurs no sin because he did not intend the improper timing.