Confirmation pop-up window is not in the center vertically in the latest Nightly.

[VitalSkib]

Hi.
With one of the latest FF Nightly updates, they "broke" something and now this pop-up confirmation window is not centered vertically, as it was usually.
Although it works correctly in a regular (Stable) build.
So, is there any chance to fix it somehow?
Check the attached images to understand what I mean.
Thanks in advance.