title: django-simple-history3.1.1 error when cascade deletion
body: <p>For a Django project I work on, I use <em>django-simple-history</em> to get a history of each of my models. Everything works very well when I create, modify or delete an object, the library generates a <code>&lt;HistoricalObject&gt;</code> each time.
  My problem is when I perform a cascade deletion.</p>
  <p>For example, I have a table B that inherits a table A. When I delete an object from my table A, it also deletes all its related objects in table B.
  <em>Django-simple-history</em> generates a <code>&lt;HistoricalObject&gt;</code> for my table A's object but for the B's it is a &quot;corrupted&quot; object with &quot;formating error&quot; because the deleted B object refers to an A object that no longer exists and this create an error.
  I can't even read the <code>&lt;HistoricalObject&gt;</code> of B when i query it. The error is :</p>
  <blockquote>
  <p>MyApp.models.tableA_object.DoesNotExist: tableA_object matching query does not exist.</p>
  </blockquote>
  <p>I haven’t found anything on the forums about it and it really blocks me, I can’t do without cascade deletion and <em>django-simple-history</em> meets all my needs except this one.</p>
  <p>Some infos :</p>
  <ul>
  <li>Django 4.0.3</li>
  <li>django-simple-history 3.1.1</li>
  <li>MySql</li>
  <li>Python 3.9.7</li>
  </ul>
  <p>Thank you for your help</p>