title: Flutter and getx: update() does not notify GetBuilder
body: <p>I have a very strange issue for my current project using Flutter and <code>getx</code> package. Short: the Notifier is not working. On <code>initState</code> from a <code>GetBuilder</code> I try to update an variable (.obs) and call <code>update()</code>, but the view knows nothing about it.</p>
  <p><strong>Reproduction code</strong></p>
  <p>GetxController:</p>
  <pre class="lang-dart prettyprint-override"><code>class HoursController extends GetxController {
    final AwController awController = AwController();
    final hours = [].obs;
  
    void loadHours({required Kunde kunde}) async {
      this.hours.assignAll([&quot;Test1&quot;, &quot;Test2&quot;]);
      update([&quot;hours&quot;]);
    }
  }
  </code></pre>
  <p>View:</p>
  <pre><code>GetBuilder&lt;HoursController&gt;(
    id: &quot;hours&quot;,
    initState: (_) {
      HoursController().loadHours(kunde: this.kunde);
    },
    builder: (controller) {
      if (controller.hours.length == 0) {
        return Container(
          child: Text(&quot;Nothing&quot;),
        );
      }
      return ListView.builder(
          shrinkWrap: true,
          physics: ClampingScrollPhysics(),
          itemCount: controller.hours.length,
          itemBuilder: (BuildContext context, int index) {
            return ListTile(
              title: Text(controller.hours[index]),
            );
          });
    },
  )
  </code></pre>
  <p><strong>Expected behavior</strong>
  After calling the function on <code>initState</code>, which changes the <code>hours</code> variable, I expect that the <code>update[&quot;hours&quot;]</code> will notify the view to refresh the state. But nothing happens. The console shows the correct data. So the variable really was refreshed, but the view was not notified about it.</p>
  <p><strong>Flutter Version:</strong>
  Flutter 2.2.3 • channel stable • <a href="https://github.com/flutter/flutter.git" rel="nofollow noreferrer">https://github.com/flutter/flutter.git</a>
  Framework • revision f4abaa0735 (8 weeks ago) • 2021-07-01 12:46:11 -0700
  Engine • revision 241c87ad80
  Tools • Dart 2.13.4</p>
  <p><strong>Getx Version:</strong>
  4.3.8</p>
  <p><strong>By the way</strong>
  I'm working with Flutter Desktop</p>