<img src="https://sojujo.smugmug.com/Other/Nitro-Screenmovies/n-8kxgNf/i-6VQGpkZ/A" alt="" />
That’s the link to the image. Which usually works on other forums.
Before I updated to the new version, I quit Nitro. Then started again and added a new folder to the left sidebar.
After reporting the bug, I quit Nitro again and just staretd it now. No more horizontal line.
From the old screenshot I can say, the width were two px on the screen, one 0,0,0 and the other 166,166,166 or opacity. If you need the screenshots, I can send them by mail.