Updating items and groupName results in error

**Describe the bug**
Trying to move or drag any item after updating both `items` and `groupName` results in an error.
`Uncaught TypeError: this.sortableGroup is undefined`

**To Reproduce**
~~~hbs

{{#each this.items as |item|}}

1. 
   {{item}}
   ↕
   

{{/each}}

The last dragged item was: {{this.lastDragged}}

Change data source
~~~

~~~js
export default class FooComponent extends Component {
@tracked lastDragged;
@tracked items = ['A', 'B', 'C'];
@tracked groupName = 'foo_01';

@action
reorderItems(itemModels, draggedModel) {
this.items = itemModels;
this.lastDragged = draggedModel;
}

@action
updateDataSource() {
this.groupName = 'foo_02';
this.items = ['D', 'E', 'F'];
}
}
~~~

1. Render component
2. See default rendered items (A, B, C)
3. Click "Change data source" button
4. See items are changed (D, E, F)
5. Try to move any given item
6. See error

**Expected behavior**
Should be able to move items after they are updated.