Playing my unnethack 5.2.0 as a Knight, I had a tamed warhorse to ride named Pet. Every time it died, I revived it with a wand of turn undead. However, a second after doing so (I had time to open menus, for example) the app would crash. If I picked up the saddle first, then revived Pet, the game was fine.
I haven't tried reproducing in wizard mode yet.
Googling for combinations of these keywords doesn't show any other issue, leading me to assume it's a port issue, not an unnethack/nethack issue