title: why I have to make empty function in react context object?
body: <p>I'm trying to understand reacjs context API from docs. In the provided example on <a href="https://reactjs.org/docs/context.html#updating-context-from-a-nested-component" rel="nofollow noreferrer">Updating Context from a Nested Component</a>  I found they created a context object like that :</p>
  
  <pre><code>export const ThemeContext = React.createContext({
    theme: themes.dark,
    toggleTheme: () =&gt; {},
  });
  </code></pre>
  
  <p>So I asked what is the role of <code>toggleTheme: () =&gt; {}</code>. I found two live example for this snippet of code, They both using the same expression of empty function/method . I tried to remove it at all to see where it affect ... and I found nothing. Every thing working good, that makes me curious to know what it doing?</p>
  
  <ul>
  <li><strong>first</strong> Live sinppet : <a href="https://codesandbox.io/s/73jkjq57lq" rel="nofollow noreferrer">https://codesandbox.io/s/73jkjq57lq</a></li>
  <li><strong>second</strong> Live sinppet : <a href="https://codesandbox.io/s/p9p4jmqkq7" rel="nofollow noreferrer">https://codesandbox.io/s/p9p4jmqkq7</a></li>
  </ul>
  
  <p>Thanks a lot...</p>