wayland/subsurface: Follow-up fixes for !3725
231874a8 is a bonus fix for a hypothetical issue I stumbled over while working on the other commits, which fix the issue reported by @swick in !3725 (comment 2098584).
231874a8 is a bonus fix for a hypothetical issue I stumbled over while working on the other commits, which fix the issue reported by @swick in !3725 (comment 2098584).