How to kill a passenger upon death of the entity it was riding on?

[golden rain]

/summon snowball ~ ~ ~ {Motion:[5.0,0.0,0.0],Passengers:[{id:"minecraft:item_display",item_display:"head",Tags:["kill_me"],item:{id:"minecraft:dirt",count:1,components:{"minecraft:item_model":"welormit:bullet"}}}]}

I just want the passenger to die once once snowball it was riding stops existing

I know that I can do something like

on projectile hit:
  loop all entities in radius 1 around snowball:
    "%loop-entity%" contains "display"
    kill loop-entity

but I'm trying to check if the loop entity isn't riding anything

[golden rain]

(item_display in just displays as "display" so I'm using this method and not loop-entity is item display nor loop-entity is display)

[outer heart]

you could try
rider/passenger of event-entity

[golden rain]

I'll try it once I'll get home