Need help with a really broken quest in Blood and Wine. Hanse Base - Mont Crane Castle

[Alin.]

So, i wanted to finish tonight all the remaining side content. Until.. i saw this. I remember completing the base when i was searching for the Grandmaster Griffin gear. I remember blowing the leader up with Aard right from the top of the base, he died, i got the cutscene with the knights returning to the base. Didn't notice that i still had the "Knight for hire" quest mark on that place. What can i do now? He's dead, he won't respawn again.

https://steamcommunity.com/sharedfiles/filedetails/?id=2676999073