If a promoted node is deleted, the listing page returns a PHP error

Problem/Motivation

If one of the promoted nodes is deleted, the listing page returns the following PHP error:

Error: Call to a member function label() on null in Drupal\vais_promos\VaisPromoListBuilder->buildRow() (line 107 of modules/contrib/vais_promos/src/VaisPromoListBuilder.php).

This is because the code doesn't do a check that the node exists before calling label() on it and there's no hook_node_delete() to clean up promotions when the associated node is deleted.

$promoContent = $this->entityTypeManager->getStorage('node')->load($entity->promo_content->target_id);
$promoReferenceLink = Link::createFromRoute($promoContent->label(), 'entity.node.canonical', ['node' => $entity->promo_content->target_id]);

Steps to reproduce

Promote a node and then delete it.

Proposed resolution

Recommend adding a check that the node exists before calling label and also adding a hook_node_delete call to delete the promotion if the node it is associated with is deleted.