EmberJS / TextField / focusOut / type number / invalidate / clear

I have a custom view named bootstrapText, like this:

import Ember from 'ember';

export default Ember.TextField.extend({
  classNames: ['form-control', 'input-md'],
  attributeBindings: ['required'],
  required: false,
  focusOut: function() {
    console.log('focusOut');
    if (Ember.isEmpty(this.get('value'))) {
      this.set('value', 0);
    }
  }
});

I'm using from the template this way:

{{view 'bootstrapText' value=numbeOfItems type='number'}}

You see, the type is "number". My observation: Ember TextField's behavior when type is set to 'number' is...: it simply wouldn't assign the inputted value to the bound variable (numberOfItems) if I input unparsable string (e.g.: xyz). So, numberOfItems stays undefined.

The problem is: Ember.TextField does not clear the field in that situation. So, the field keeps showing "xyz".

I want it to be cleared automatically, that's why I implement the focusOut method... where I set the the value to 0. But that's not what I actually want; 0 is not the same as undefined. I want to use 'undefined' as "user hasn't entered anything valid". 0 is a a valid input.

I tried: this.set('value', undefined); ... but of course it has no effect to the display (no change detected; undefined -> undefined).

I tried also: this.set('value', 0); followed by this.set('value', undefined); .... No luck.

Do you know the solution / correct technique for this?

Thanks, Raka