Again: article without images gives a error in .

I checked the video, but one step is missing.

What is essential is that you create an article where the inage is missing (or deleted).

So enter as article content:
<h1>Edward in de lijst 'eeuwige roem' !</h1>
<p><img src="images/nieuws/2021/Rotterdam2021-5.jpg" alt="Rotterdam2021 5"><br><em>Foto: Rieka bij 41km punt; 'Edward in zijn pijngrot'</em><br><br>In de <a href="www.runnersworld.com/nl/nieuws/a38620429...honranglijsten-2021/" target="_blank" rel="noopener noreferrer">Nationale Marathonranglijst 2021 zoals gepubliceerd in de februari-editie van Runner's World staat één LBer.

So image: images/nieuws/2021/Rotterdam2021-5.jpg is not there in your system.

The Custom Default Thumbnail is in my case. You can select any, when a # is in the custom default.
images/logos/banners/LB-logo2020.png#joomlaImage://local-images/logos/banners/LB-logo2020.png?width=480&height=480

Then the error pops up.
The solution is given above.

Regards,
Peter