What is the ruling regarding a fasting person swallowing remnants of the pre-dawn meal (suhoor) found in their mouth after waking up?

Eating is among the nullifiers of fasting. This includes swallowing food remnants caught between the teeth if the fasting person was able to remove them but swallowed them intentionally; in such a case, their fast is nullified. However, if they slipped down their throat and were swallowed without the fasting person being able to remove them, or if they swallowed a tiny amount that cannot be avoided, then their fast is valid because they had no choice in the matter.