Systray legacy icons are drawn with offset

Systray legacy icons are drawn such as if distance from the left is doubled.

If systray is the leftmost element on the panel, it looks OK.

When I start adding separators (or any item) before systray, legacy icons are shifted to the right up to completely disappearing. Status notifiers are not affected.

xfce4-panel 4.20.3, X11, Arch Linux

I've done some investigation. Fixed it for myself, will create a merge request.