Fixed #30302 -- Fixed forms.model_to_dict() result if empty list of fields is passed.

django/forms/models.py

@@ -83,7 +83,7 @@ def model_to_dict(instance, fields=None, exclude=None):
     for f in chain(opts.concrete_fields, opts.private_fields, opts.many_to_many):
         if not getattr(f, 'editable', False):
             continue
-        if fields and f.name not in fields:
+        if fields is not None and f.name not in fields:
             continue
         if exclude and f.name in exclude:
             continue

tests/model_forms/tests.py

@@ -1814,6 +1814,7 @@ class ModelOneToOneFieldTests(TestCase):
 
         bw = BetterWriter.objects.create(name='Joe Better', score=10)
         self.assertEqual(sorted(model_to_dict(bw)), ['id', 'name', 'score', 'writer_ptr'])
+        self.assertEqual(sorted(model_to_dict(bw, fields=[])), [])
         self.assertEqual(sorted(model_to_dict(bw, fields=['id', 'name'])), ['id', 'name'])
         self.assertEqual(sorted(model_to_dict(bw, exclude=[])), ['id', 'name', 'score', 'writer_ptr'])
         self.assertEqual(sorted(model_to_dict(bw, exclude=['id', 'name'])), ['score', 'writer_ptr'])