title: isIdleTimerDisabled = true works but setting back to false won't dim the screen again
body: <p>This is an iOS 13+ only app.</p>
  
  <p>I want to let the user decide if the main view controller of my app prevents screen dimming or not. That view controller has in viewDidAppear:</p>
  
  <pre><code>UIApplication.shared.isIdleTimerDisabled = GlobalSettings.keepScreenOn // my setting variable
  </code></pre>
  
  <p>In viewDidDisappear it has:</p>
  
  <pre><code>UIApplication.shared.isIdleTimerDisabled = false
  </code></pre>
  
  <p>The intention is that whenever this VC is not on screen, screen dimming should work normally. While testing the feature, I see that once I turned the setting on, the screen won't dim again whether I let it sit in another VC, and whether I turn the setting off again.</p>
  
  <p>Any ideas??</p>