rootston: Also iterate layer shell popups
rootston: Also iterate layer shell popups

Broken by 62fd03a7beb18da6c4a5929e38739cf2199dfa79

Closes: #1631

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