Zombies can't attack villagers that are in boats

Steps to Reproduce: 

1. Open a world and summon 2 villager

2.  Push them on a boat to make the boat full

3. Summon a zombie, which will try to attack the villager

Observed Results: 

The zombie walks towards the villagers. As soon as it walk over the boat, it can’t attack the villagers

Expected Results: 

Zombie should attack villagers as usual no matter whether the villagers are on boat