Model Update ignores null

Hi, I have a weird problem, I don't know if I'm doing something wrong or it is a bug.
I have a soft delete for customers. CustomerModel and Customer Entity.
Database field: customer_deleted: 1,0, NULL (Default:NULL)
Code:

PHP Code:

 
$customerModel = new CustomerModel();
 $customer = new Customer();
$customer->customer_deleted = null;
$customer->customer_deleted_at = date('Y-m-d H:i:s');
 $customerModel->update($customer_id, $customer); 


This code update the date but does not set customer_deleted to NULL, it ignores it.

If I use array instead of entity object, It works, updates date and set deleted = null

PHP Code:

 
 $customerModel = new CustomerModel();
$array = [
     'customer_deleted' => null,
     'customer_deleted_at' => date('Y-m-d H:i:s')
 ];
$customerModel->update($customer_id, $array); 


 

Why passing data as entity object does not work?
Maybe codeigniter ignore data = null when calling update()?

Thank you