Empty object value in create does not override factory default

[serhalp]

Given this factory:

const fact = unionized.factory({foo: {bar: 3}})

Creating an object like so:

fact.create({foo: {}})

The expected output object is

{
  "foo": {}
}

but the result is

{
  "foo": {
    "bar": 3
  }
}

This works as expected with {foo: null} and {foo: undefined}.