Avoid TypeError if config entity dependencies are NULL

Problem/Motivation

We noticed an error on the 10.3 update when trying to resave config entities, the affected sites has some invalid definitions with NULL instead of an empty array, which results in:

[error]  TypeError: array_intersect_key(): Argument #1 ($array) must be of type array, null given in array_intersect_key() (line 378 of /var/www/html/docroot/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php) #0 /var/www/html/docroot/core/lib/Drupal/Core/Config/Entity/ConfigEntityBase.php(378): array_intersect_key(NULL, Array)

Steps to reproduce

Proposed resolution

Add a ?? [] to avoid this. There might be other checks later on, didn't get that far yet.

Remaining tasks

User interface changes

API changes

Data model changes

Release notes snippet