Fixed #11277 -- Hid labels of fields with HiddenInput widget in admin forms.

Thanks bartTC for the report.

tests/admin_views/models.py

@@ -704,3 +704,12 @@ class FilteredManager(models.Model):
 
     pk_gt_1 = _Manager()
     objects = models.Manager()
+
+class EmptyModelVisible(models.Model):
+    """ See ticket #11277. """
+
+class EmptyModelHidden(models.Model):
+    """ See ticket #11277. """
+
+class EmptyModelMixin(models.Model):
+    """ See ticket #11277. """