Empty dropdown for chained field

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[x ] This issue is not about installing previous versions of django-smart-selects older than 1.2.8. I understand that previous versions are insecure and will not receive any support whatsoever.
[x ] I have verified that that issue exists against the master branch of django-smart-selects.
[x ] I have searched for similar issues in both open and closed tickets and cannot find a duplicate.
[ x] I have debugged the issue to the smart_selects app.
[ x] I have reduced the issue to the simplest possible case.
[ x] I have included all relevant sections of models.py, forms.py, and views.py with problems.
[ x] I have used GitHub Flavored Markdown to style all of my posted code.

Steps to reproduce

This my my models.py:

from smart_selects.db_fields import ChainedForeignKey

class Funder(models.Model):
    name = models.CharField(max_length=200)
    scheme = models.ManyToManyField('Scheme', blank=True, related_name='funders')

class Scheme(models.Model):
    name = models.CharField(max_length=200)

class Project(models.Model):
    title = models.CharField(max_length=200)
    funder = models.ForeignKey(Funder, on_delete=models.PROTECT, null=True, blank=True)
    scheme = ChainedForeignKey(
        Scheme,
        chained_field="funder",
        chained_model_field="funder",
        show_all=False,
        auto_choose=True,
        sort=True, null=True, blank=True)

In my Django admin backend, go to any project, existing or new. Select a funder from the funder dropdown.

Actual behavior

There is no scheme in the scheme dropdown, although that specif funder does indeed contain one or more scheme.

Expected behavior

The scheme dropdown should show all the schemes linked to that specific funder.

This is with smart_selects v. 1.7.1 (installed via pip install git+https://github.com/jazzband/django-smart-selects.git) and Django 5.0.4.

It used to work with previous versions.

jazzband / django-smart-selects