White bar at the bottom of the screen when maximized

[Waltzabout]

When I have Pale Moon maximized, there is a 1 pixel tall white line going across the bottom of the screen.
It is not there when in windowed mode, nor when other programs are maximized, this only happens with Pale Moon.
Here is an example image:

and one zoomed in so you can see it better:


Any help would be appreciated, the browser still works fine, but it can be a bit annoying on websites with a dark background.