[Checkout UI] Selling Plan Crashes Express Checkout Functionality

[gidizim]

In Shopify Checkout UI, when applying a selling plan on the checkout page, if the store has express checkouts (such as Shop Pay, Google Pay, or PayPal) installed, they all crash.

Although the selling plan is still applied, users are unable to use the express checkouts. Additionally, if a user decides to use an express checkout like Shop Pay and is already signed in, applying the selling plan afterwards still crashes and reroutes with an error to a new checkout page without the express checkouts. The type of selling plan applied involves one payment now and another in the future.

It's worth noting that the issue doesn't seem to be limited to selling plans applied at the point of checkout. Even when generating a checkout with a selling plan applied to a product, no express checkouts are available to the user. In essence, all express checkouts don't work when selling plans are involved.

Steps to Reproduce:

1. Install express checkouts on your shop.
2. Apply a selling plan to a product and proceed to checkout.
3. Observe that the express checkouts aren't visible.

Expected Behavior: The expected behavior is that express checkouts should be visible and usable when the cart has a selling plan applied to it.

Additional Context: The code causing the crash is related to applyCartLinesChange. 

Please see reference to issue in Github - https://github.com/Shopify/ui-extensions/issues/1491