title: How to check tabController for null?
body: <p>Can you please tell me how can I check tabController for null:</p>
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-js lang-js prettyprint-override"><code>final CupertinoTabController? tabController = CupertinoTabController(initialIndex: 0);</code></pre>
  </div>
  </div>
  </p>