Check EntityPublishedInterface before calling isPublished()

The sector_utils module adds a class to all unpublished entities via hook_ds_pre_render_alter(), but not all entities have a published/unpublished status with recent changes to Drupal core.

This throws an undefined method if an entity that doesn't implement the publishable trait is rendered in any view mode other than "full".

An example from the entity provided by the profile module:

Error: Call to undefined method Drupal\profile\Entity\Profile::isPublished()

The fix is simply to check for EntityPublishedInterface before calling the method.