Issue in edit case in multiple selected dropdown.

### Version of x-select:
3.1.1
### Ember Version / Ember CLI Version:

**Ember Version:**
3.0.0
**Ember CLI Version:**
~3.0.2
### Expected Behavior
When I am trying to edit the multiple selected checkbox it gives blank array. It should be like if the form field is set to ['10001','10002','10003'] in edit form and I click on 10002 it should be de-select and the remaining value ['10001','10003'] should go in the API request.

### Actual Behavior
Currently, when I deselect any value then all value is going to blank.

### Steps To Reproduce:
1. Try to use in edit form (Multiple select).
2. Try to de-select the element from edit form.
3. You will get a blank array instead of getting the filled array.
Like this:
['1','2','3']

Now try to deselect 2 from the array. '2'
You should get ['1','3'] but you get [''] and if you double click on '2' you will get ['2'] in array.