1 pixel wide dead line when hovering over global menu

[bidinou]

Hi !
When activating the global menu but moving my mouse to the extreme top of the screen and clicking, and then moving the mouse cursor horizontally, the focus is lost by the menu, as if there was a 1 pixel dead line at the top of the screen.

I have to move the mouse down a little to activate the other menu entries.
Screenshot of the issue : https://framapic.org/9oVsu7iQGfuy/NBjKBO9WfUbJ.png