CSS Gives Vertical White Line when the window is in Restore Down

After quite a few searches, I found the Wordpress theme I was looking for, but it seems it has a problem and its developer is not answering my emails.
I had a look in the CSS but I couldn't figure it out because I'm not good with CSS, I barely know a few basic things about it but not enough to solve this problem.

Ok, so here's the problem. The theme looks ok when the window (with all browsers, Firefox, Chrome, IE, etc) is on full screen, but if you click on the Restore Down button (TOP RIGHT CORNER), the button in the middle of Minimize and Close, a giant vertical white line appears on the right sidebar.

Here's the theme: http://www.magpress.com/wordpress-themes/Revano.html

Just click on Demo/Preview then make your browser's window small by clicking on Restore Down.

I've also included 2 screenshots, why is that line there? Can someone have a look in the CSS and tell me how to remove it?

Thanks