title: React defaultProps doesn't fill missing object props
body: <p>If I have a component that its propTypes are the following</p>
  
  <pre><code>import React, { Component } from 'react'
  import propTypes from 'prop-types'
  
  class MyComponent extends Component {
      ///
  }
  
  MyComponent.propTypes = {
      hidden: propTypes.string.isRequired,
      items: propTypes.object,
      attributes: propTypes.array
  }
  
  MyComponent.defaultProps = {
      hidden: false,
      items: {},
      attributes: ['baz', 'qux']
  }
  </code></pre>
  
  <p>If my component is called like this </p>
  
  <p><code>&lt;MyComponent hidden={true} items={[value: 'foo', label: 'bar']} /&gt;</code> </p>
  
  <p>I would like to expect that <code>props.attributes</code> is populated with the <code>defaultProps</code> values since it's value is not defined. Is this something that can be achieved (easily)?</p>