So? Hit the cancel button when you close it - you have to be right there to close it after all.
TBH, I do this too, because I hate putting in some milk to warm for cereal and getting out warm milk flavoured with and smelling of the curry we warmed last night.
Anytime the microwave oven is used for aromatic food or any meal with flavouring, leave the door open.
The idea of warming milk for cereal has never crossed my mind.
Workaround: slightly ajar as default idle state for silent operation and intercept immediately before completion.
That's actually a problem with my dishwasher, which can't be left slightly open (it always closes shut), and me being a single, so it takes time to get a full machine. If I want to prevent mold I either have to start the dishwasher half empty (which is counterintuitive) or to collect the dirty dishes outside the dishwasher until enough have accumulated to fill it. But then you have all the dirty dishes lying around. Argh!