Chips producing error

I have a simple paper-chips component that pulls selectedSites:
```
{{#paper-chips content=selectedSites as |item|}}
{{item.siteDisplayName}}
{{/paper-chips}}
```

When a site gets added to the `selectedSites` array, the following error is produced:

```
Assertion Failed: You modified "siteDisplayName" twice on in a single render. It was rendered in "component:paper-chips" and modified in "component:paper-chips". This was unreliable and slow in Ember 1.x and is no longer supported. See https://github.com/emberjs/ember.js/issues/13948 for more details.
Error
```