django admin problem used model inheritance

[osanha@…]

for example,

class Parent(models.Model):
    s = models.ForeignKey('self', null=True, blank=True)
    a = models.TextField()
    
class Child(Parent):
    b = models.TextField()

1.

When Child create in django admin, Parent reference id is not need. It should be inserted automatically.
But, admin complain it is necessary.

So, after I add one dummy Parent, Child was created successfully with it's own automatically created parent's ID.
So, number of Parent was two.
Every create Child, choice dummy Parent is needed.

2.

like above code.
when delete Child or Parent, error occured about Child's s_id.

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these error was begined at 0.97-pre-SVN-8007
as I know, previous version is not shown these errors.