FormState.List not working with arrayUtils.push

[lucasfrosty]

Overview

Probably related to #519
When creating a new instance of something into an array, the component just 💥

The arrayUtils.push is working just fine, so i guess is something related to how the component now is handling the updating/changes when this prop updates, which changed after the commit that 🔥 lodash.

Consuming repo

On https://github.com/shopify/web, but that's also reproducible on this codesandbox that i got from the docs, just click on Add variant there and you'll see things exploding.

cc @TzviPM @TheMallen

[lucasfrosty]

Fixed on #531
Thanks @marina101 for the fix!!