I don’t see a conflict, they not me an umpire for their games, but barring any inappropriate conduct related to their umpiring duties, I don’t see a problem.
there are a number of these going on, with no context given. How long have they known each other? Are childhood or longtime friends no longer allowed to dine together? It’s seems like trying to stir up drama for no reason. If it’s an umpire that hs any questionable calls relating to a person, perhaps a question could be raised, but also keep in mind no one in the badminton world is paid enough to really make it worth to bribe an umpire, even if it was considered.