[3.2.x] Fixed #32863 -- Skipped system check for specifying type of a…

…uto-created primary keys on models with invalid app_label.

Regression in b5e12d4.

Thanks Iuri de Silvio for the report.

Backport of 7a9745f from main

django/db/models/base.py

@@ -1306,6 +1306,7 @@ def _check_default_pk(cls):
                 cls._meta.pk.remote_field.parent_link
             ) and
             not settings.is_overridden('DEFAULT_AUTO_FIELD') and
+            cls._meta.app_config and
             not cls._meta.app_config._is_default_auto_field_overridden
         ):
             return [

docs/releases/3.2.5.txt

@@ -20,3 +20,6 @@ Bugfixes
 * Fixed a regression in Django 3.2 that caused a migration crash on MySQL
   8.0.13+ when adding nullable ``BinaryField``, ``JSONField``, or ``TextField``
   with a default value (:ticket:`32832`).
+
+* Fixed a bug in Django 3.2 where a system check would crash on a model with an
+  invalid ``app_label`` (:ticket:`32863`).

tests/check_framework/test_model_checks.py

@@ -403,6 +403,13 @@ class Child(Parent):
 
         self.assertEqual(checks.run_checks(app_configs=self.apps.get_app_configs()), [])
 
+    def test_skipped_on_model_with_invalid_app_label(self):
+        class Model(models.Model):
+            class Meta:
+                app_label = 'invalid_app_label'
+
+        self.assertEqual(Model.check(), [])
+
     def test_skipped_on_abstract_model(self):
         class Abstract(models.Model):
             class Meta: