Error while rendering empty record from db

[maartends]

I have one model (RelTag) with only two fields, both of which are nullable. When an empty record is being created through the fa.jquery /admin following error is produced when later trying to open this empty record for editing.

I am using:

• pyramid 1.4
• fa.jquery 0.9.5
• pyramid-formalchemy 0.4.3
• SQLAlchemy 0.7.6
  on Postgresql 8.4.

TypeError: coercing to Unicode: need string or buffer, NoneType found

• Expression: "unicode(request.model_instance)"
• Filename: ... uery-0.9.5-py2.6.egg/fa/jquery/templates/admin/master.pt
• Location: (42:31)
• Source: tal:replace="unicode(request.model_instance)"/>
  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
• Arguments: fs: <FieldSet - at 0x4729d10>
  model_plural: RelTags
  actions: {...} (1)
  model_label: RelTag
  breadcrumb: <Actions - at 0x4a6d100>
  repeat: {...} (0)
  renderer_name: pyramid_formalchemy:templates/admin/edit.pt
  F_: <function translate at 0x4a701b8>
  id: 3
  req: <Request - at 0x4700650>
  renderer_info: <RendererHelper - at 0x428c610>
  request: <Request - at 0x4700650>
  context: <RelTagCustomModel_admin_edit_GET 3 at 0x4729310>
  model_class: <I18NModel RelTag at 0x4729590>
  main: <PageTemplateFile - at 0x471a5d0>
  model_name: RelTag
  view: <ModelView - at 0x4729510>