Accessing HistoricForeignKey relation after .as_instances() throws error

[tahme]

Describe the bug

According to the documentation, these two should be equivalent

RankedDocument.history.as_of(t1)
RankedDocument.history.filter(history_date__lte=t1).latest_of_each().as_instances()

but if you use .as_instances() and try to access an object related through a HistoricForeignKey, an error is thrown:

ValueError("Cannot use None as a query value")

The stack trace points to manager.py, line 202, in as_of:

    queryset = self.get_queryset().filter(history_date__lte=date)

To Reproduce
Steps to reproduce the behavior:

1. Create model with HistoricForeignKey, e.g.

class Poll(models.Model):
    question = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published', default=timezone.now())
    history = HistoricalRecords()

class Choice(models.Model):
    poll = HistoricForeignKey(Poll, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)
    history = HistoricalRecords()

2. Create a Poll and add a Choice

choice = Choice.objects.create(poll=Poll.objects.create())

3. Get an instance from history using as_instances() and try to access .poll

choice.history.as_instances().first().poll # raises error
choice.history.first().instance.poll # works

I did notice that choice.history.first().instance has no attribute _history._as_of but choice.history.as_instances().first() has _history._as_of == None. I think this causes HistoryManager.as_of to be called with date=None.

Expected behavior
Accessing related object works after using .as_instances().

Environment (please complete the following information):

• OS: Linux Mint 21.2
• Django Simple History Version: 3.4.0
• Django Version: 4.2.6
• Database Version: sqlite3