Broken PNG

[Chemeindefer]

Hello. It's a nice repo but there's a problem. I can see the webcam at the top right of the screen. But the rest of the screen is black. I wondered if it was related to my recording and I tried a few other recordings and the situation is the same. When I looked at the image files created later, I saw that they were corrupt. There is no problem with SVGs, I checked them. I thought that the _render_slide method was causing corrupted PNG files, so I made some changes here, but I was not successful. Your help would be great.