[4.0.x] Fixed #33547 -- Fixed error when rendering invalid inlines with readonly fields in admin.

Regression in de95c826673be9ea519acc86fd898631d1a11356.

Thanks David Glenck for the report.
Backport of 445b075def2c037b971518963b70ce13df5e88a2 from main

1 files changed, 4 insertions, 0 deletions

diff --git a/tests/admin_inlines/models.py b/tests/admin_inlines/models.py
index 47c5b91828..a8d2ee02e1 100644
--- a/tests/admin_inlines/models.py
+++ b/tests/admin_inlines/models.py
@@ -5,6 +5,7 @@ import random
 
 from django.contrib.contenttypes.fields import GenericForeignKey
 from django.contrib.contenttypes.models import ContentType
+from django.core.exceptions import ValidationError
 from django.db import models
 
 
@@ -204,6 +205,9 @@ class Question(models.Model):
     text = models.CharField(max_length=40)
     poll = models.ForeignKey(Poll, models.CASCADE)
 
+    def clean(self):
+        raise ValidationError("Always invalid model.")
+
 
 class Novel(models.Model):
     name = models.CharField(max_length=40)