how can i pass an empty object as props to a createupdate form?

Default accepts a factory function:

props: {
  foo: {
    type: Object,
    default: () => ({})
  }
}

See Prop Validation.

Relevant bit:

...
  // Object or array defaults must be returned from  
  // a factory function  
  default: function () {  
    return { message: 'hello' }  
  }
...