xdg_shell stable: allow zero-sized positioner set_anchor_rect
xdg_shell stable: allow zero-sized positioner set_anchor_rect

This is a protocol difference with xdg-shell-unstable-v6

SirCmpwn/wlroots,swaywm/wlroots,ascent12/wlroots,ascent12/wlroots,swaywm/wlroots