OrderItemsTaxesApplicator breaks when items are removed

[aleho]

When items are removed from a Doctrine ArrayCollection, the indexes leave holes.

OrderItemsTaxesApplicator iterates over the items using an index, causing access to unset array keys:

RefundPlugin/src/TaxesApplicator/OrderItemsTaxesApplicator.php

Line 79 in 7016d49

foreach ($item->getUnits() as $index => $unit) {

A simple fix would be to either use $item->getUnits()->getValues() or (less elegant) use a counter variable as seen in Sylius 1.9.

This is critical in my opinion, as it breaks all setups with RefundPlugin, so possibly also Plus.