model.save() error

the following action:

    deleteCategory: function() {
      var self = this;
      var removedCategory = this.get('model');
      removedCategory.deleteRecord();
      removedCategory.save().then(function(result) {
        var org = removedCategory.get('organization');
        org.get('categories').removeObject(result);
        org.save().then(function() {
          self.transitionToRoute('organization', org);
        });
      });
    }


generates the following error:

Error: Assertion Failed: calling set on destroyed object
    at new Error (native)
    at Error.Ember.Error (http://localhost:8001/vendor/ember/ember.js:844:19)
    at Object.Ember.assert (http://localhost:8001/vendor/ember/ember.js:73:11)
    at set (http://localhost:8001/vendor/ember/ember.js:2969:9)
    at Ember.Object.extend.hasManyDidChange (http://localhost:8001/vendor/ember-data/ember-data.js:5951:11)
    at null.<anonymous> (http://localhost:8001/vendor/ember-data/ember-data.js:5940:18)
    at http://localhost:8001/vendor/ember/ember.js:3368:16
    at Object.OrderedSet.forEach (http://localhost:8001/vendor/ember/ember.js:3211:10)
    at Object.Map.forEach (http://localhost:8001/vendor/ember/ember.js:3366:10)
    at Ember.Object.extend.reloadHasManys (http://localhost:8001/vendor/ember-data/ember-data.js:5937:23) ember.js:3461
logToConsole ember.js:3461
Ember.RSVP.onerrorDefault ember.js:16897
__exports__.default.trigger ember.js:8717
Promise._onerror ember.js:9441
publishRejection ember.js:9848
DeferredActionQueues.flush ember.js:5893
Backburner.end ember.js:5984
Backburner.run ember.js:6023
Ember.run ember.js:6426
hash.success ember-data.js:1523
fire jquery.js:1037
self.fireWith jquery.js:1148
done jquery.js:8074
callback jquery.js:8598
Uncaught Error: Assertion Failed: Error: Assertion Failed: calling set on destroyed object ember.js:73
Ember.assert ember.js:73
Ember.RSVP.onerrorDefault ember.js:16898
__exports__.default.trigger ember.js:8717
Promise._onerror ember.js:9441
publishRejection ember.js:9848
DeferredActionQueues.flush ember.js:5893
Backburner.end ember.js:5984
Backburner.run ember.js:6023
Ember.run ember.js:6426
hash.success ember-data.js:1523
fire jquery.js:1037
self.fireWith jquery.js:1148
done jquery.js:8074
callback