TypeError: backend.models.form.Form() argument after ** must be a mapping, not NoneType

[sentry]

Sentry Issue: FORMS-BACKEND-H

TypeError: backend.models.form.Form() argument after ** must be a mapping, not NoneType
(9 additional frame(s) were not displayed)
...
  File "starlette/routing.py", line 266, in handle
    await self.app(scope, receive, send)
  File "starlette/endpoints.py", line 42, in dispatch
    response = await handler(request)
  File "spectree/spec.py", line 166, in async_validate
    return await self.backend.validate(
  File "spectree/plugins/starlette_plugin.py", line 100, in validate
    response = await func(*args, **kwargs)
  File "backend/routes/forms/form.py", line 56, in get
    form = Form(**await request.state.db.forms.find_one(filters))