Knockout JS - How to return empty strings for observable fields

Im building a CRUD system where users can add, delete and edit data from a simple table. I have a modal form that is used to show additional details and also adding new incidents. Currently the modal form loads correctly for editing but has issues when trying to add a new incident.

After some debuging it seems that the issue comes from this line:

self.currentIncident(null);

This breaks my modal form because my observable is coming back null (obviously). I was hoping that it would return something like the following:

"ID": "",
"Description": "",
"Incident": ""

I believe this is why my modal is crashing since my modal is confused with the return. Would someone know of an easy method to return empty strings?

  self.AddNewIncident = function() {
    var id = this.ID;
    self.showModal(true);
    self.currentIncident(null);
  };

Here is jsfiddle: http://jsfiddle.net/rqwku4kb/12/

Put {} instead of null like this:

self.currentIncident({});

Check Fiddle