api3: 500 on non-existent provider when not listing

[nyiyui]

'ObjectNew' should either include a `serializer_class` attribute, or override the `get_serializer_class()` method.

thanks to @JasonLovesDoggo

[JasonLovesDoggo]

fixed in 3691fbeed759920cf3e52aeb563e98b80bac5f3b