subject_id is null when deleting a pivot model

[RMK147]

Describe the bug
I'm using the spatie/laravel-permission package and to track the changes I have created the below pivot model:

<?php

namespace Modules\Auth\Models;

use Illuminate\Database\Eloquent\Relations\MorphPivot;
use Spatie\Activitylog\Traits\LogsActivity;
use Spatie\Activitylog\LogOptions;

final class RoleUser extends MorphPivot
{
    use LogsActivity;

    public $incrementing = true;

    public function getActivitylogOptions(): LogOptions
    {
        return LogOptions::defaults()
            ->logAll()
            ->logOnlyDirty();
    }
}

And I have the following on my user model:

use LogsActivity, HasRoles {roles as protected spatRoles;}

public function roles(): BelongsToMany
{
    return $this->spatRoles()->using(RoleUser::class);
}

The subject_id is populated when a role is assigned to a user, now that I added $incrementing = true, but it is still null when a role is removed from the user.

To Reproduce
Things needed to reproduce the error.

Assign roles to a user, and the subject_id is populated as expected. Remove roles from a user, and the subject_id is null. For example:

id	log_name	description	subject_type	event	subject_id	causer_type	causer_id	properties	batch_uuid	created_at	updated_at
50	default	created	Modules\Auth\Models\RoleUser	created	22	Modules\Auth\Models\User	1	{"attributes": {"id": 22, "role_id": 6, "model_id": 7, "model_type": "Modules\\Auth\\Models\\User"}}	7e08874b-cef0-453d-86f3-e86cbe4a13a2	2024-10-09 16:05:44	2024-10-09 16:05:44
51	default	deleted	Modules\Auth\Models\RoleUser	deleted	NULL	Modules\Auth\Models\User	1	{"old": {"role_id": "6", "model_id": 7, "model_type": "Modules\\Auth\\Models\\User"}}	298f4384-5665-4dd0-969a-f8a0f43e157d	2024-10-09 16:06:07	2024-10-09 16:06:07

Expected behavior
The subject_id should not be null when removing a role from a user.

Versions (please complete the following information)

• PHP: 8.3
• Database: MySQL 8.3.0
• Laravel: 11.26.0
• Package: 4.8.0