growTextarea may be called against destroyed component

Using `1.0.0-beta.2`, I had the following error reported to sentry:

> Cannot read property 'addClass' of undefined

From the `growTextarea` method.

The code looks like this:

```javascript
let inputElement = this.$('input, textarea');
inputElement.addClass('md-no-flex').attr('rows', 1);
```

We probably just miss a check against 'isDestroying' and 'isDestroyed' before trying to apply `growTextarea`.

Start by locating the `growTextarea` method and read how it is invoked during component teardown. Reproduce or trace the reported `addClass` error, then verify that the method no longer operates on a destroyed component and that the existing behavior remains intact.

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