Fixed #24525 -- Fixed AssertionError in some complex queries.

Thanks Anssi Kääriäinen for providing the solution.

tests/queries/models.py

@@ -49,6 +49,7 @@ class Tag(models.Model):
 class Note(models.Model):
     note = models.CharField(max_length=100)
     misc = models.CharField(max_length=10)
+    tag = models.ForeignKey(Tag, models.SET_NULL, blank=True, null=True)
 
     class Meta:
         ordering = ['note']