Fixes #289

[CasperTDK]

Credit goes to @pandamouse

[brianfeister]

Thanks @CasperTDK but you've got a failing test there. Please fix that or think about how the test should be different before we proceed.

[pandamouse]

Ok What if we change the test to say only set the model to an array AFTER an item is selected...
https://github.com/angular-ui/ui-select/blob/master/test/select.spec.js#L1126-L1133

it('should set model as an empty array if ngModel isnt defined after an item is selected', function () {

  // scope.selection.selectedMultiple = [];
  var el = createUiSelectMultiple();
  expect(scope.selection.selectedMultiple instanceof Array).toBe(false);
  clickItem(el, 'Samantha');
  expect(scope.selection.selectedMultiple instanceof Array).toBe(true);
});