Error in TaskListBuilder when referenced entities are deleted

Problem/Motivation

When visiting /admin/config/gdpr/tasks, a fatal error occurs if a GDPR Task entity references a deleted user, bundle, or requester.

Error: Call to a member function label() on null in Drupal\gdpr_tasks\TaskListBuilder->buildRow()

Proposed resolution

Add null checks to avoid errors and display fallback labels like “Deleted user”, “Deleted bundle”, or “Unknown” for missing references.