Menus are detached if scrolled down

[Nemo157]

To reproduce, scroll down slightly then open a top-menu, the further you scroll the further down it goes and eventually goes off screen.

Happens for me on Firefox 103.0.1 and 103.0.2 on Windows, but not on Edge.

[syphar]

@euphemism could this be a bug in #1782 ? cc @GuillaumeGomez

[GuillaumeGomez]

Yes, it definitely comes from #1782. I'll send a fix shortly.

[euphemism]

Oh, huh. Sorry about that. Not something I had come across when poking around with my changes.