Splash potions of Harming do not damage endermen riding boats or minecarts

When throwing a splash potion of Harming to an enderman riding a boat/minecart, the enderman does not take damage.

Steps to reproduce:

1. Spawn an enderman riding a boat with the following command:

   /summon minecraft:oak_boat ~ ~ ~ {Passengers:[{id:"minecraft:enderman"}]}

2. Throw a splash potion of Harming to the enderman.

Observed result:

The enderman does not take damage.

Expected result:

The enderman should take damage.