Form submission error when nested fields

When I submit a form with nested fields, I receive this error:

AttributeError at /customer-invoices/
'NoneType' object has no attribute '_meta'

[...]

File "/app/djangoldp/models.py" in resource_id
  32.         view_name = '{}-detail'.format(instance._meta.object_name.lower())

Here is what I send

{
"@context":"http://owl.openinitiative.com/oicontext.jsonld",
"@graph":[
  {
    "@id":"./",
    "http://happy-dev.fr/owl/#batches":{"@id":"_:b191"},
    "http://happy-dev.fr/owl/#identifier":321,
    "http://happy-dev.fr/owl/#title":"Nouvelle facture",
    "http://happy-dev.fr/owl/#tvaRate":20
  },
  {
  "@id":"_:b191",
  "http://happy-dev.fr/owl/#title":"test batch"
  }
]}