Webpage turns black in WebEngine Content Manipulation example

In the WebEngine Content Manipulation example, the loaded webpage may turn completely black when performing different actions. This does not happen with the browser itself, but only with the webpage that is being displayed by the browser. I have only been able to reproduce this behavior by left-clicking the full screen button of the application window, and it happens very rarely. The webpage goes back to normal when interacting with the browser, or when resizing the application window.

Steps to reproduce:

After running the application, immediately try to enter full screen by left-clicking the full screen button of the application window. It may happen that the webpage turns black instantly. If not, try to repeatedly left-click the full screen button of the application window, going in and out of full screen, until the webpage turns black.