Description of Bug:
Overlaying an HTML file which contains static text, image and a call to a CSS file. There is no scripting within the HTML file.
Html filename: düsseldorf.html
Image filename: düsseldorf.png
In Shotcut, the HTML filter loads, if you open the WYSIWYG editor it looks fine, the filter overlay is visible in the playback window.
However when you export the video, you get a white screen. This can be fixed by removing the accents/diacritics from both filenames.
Either both the image preview and export fail or both work.