The constitution is pretty clear on this isn't it? Unless there's another article that specifically addresses expiration of presidential powers during martial law that i missed, claiming that Ukranian constitution does not allow presidential elections in time of war is a straight up propaganda and a blatant lie made to mislead the masses.
You found the constitution and even quoted something about 'martial law' and did not research it? I mean the martial law thing. It is written down like in every halfway sane country.