Gittin 28B

שמא מת לא חיישינן, שמא ימות חיישינן.

There is a different distinction: We are not concerned that perhaps he has already died, which is why the Mishnah rules that she may continue to partake of teruma. However, in the case of one who stipulates that the bill of divorce will take effect one hour before his death, we are concerned that perhaps he will die at an unknown moment in the future and she will no longer be permitted to partake of teruma.

אמר ליה רב אדא בר מתנה לרבא: והא נוד דכשמא ימות הוא, ופליגי! אמר רב יהודה מדסקרתא: שאני נוד דאפשר דמסר ליה לשומר.

Rav Adda bar Mattana said to Rava: But the concern in the case of the wineskin is that it might burst before one is able to separate the teruma and tithes, which is similar to the concern that perhaps he will die, as both are concerns with respect to the future, and R' Yehuda and R' Meir disagree. Rav Yehuda of Diskarta said: A wineskin is different, as it is possible to give it to a watchman who will protect it from bursting, which is why R' Meir is not concerned that it might burst. This reasoning does not apply to the concern that the husband might die.

מתקיף לה רב משרשיא: ערביך ערבא צריך! אלא אמר רבא: שמא מת ⁠– לא חיישינן, שמא ימות ⁠– תנאי היא.

Rav Mesharshiyya objects to this answer: Your guarantor himself needs a guarantor, as there is no way of knowing that the guardian will not be negligent, so the wineskin may burst. Rather, Rava said: Everyone agrees that we are not concerned that perhaps he has already died, in accordance with the Mishnah here. As to the issue of whether there is a concern that perhaps he will die, as in the case of the baraita, this is a dispute between tanna’im.