Fix subsurface deletion segfault

Author: serebit

src/surface/subsurface.cpp

@@ -26,7 +26,6 @@ Subsurface::Subsurface(Surface& parent, wlr_subsurface& subsurface) noexcept
 }
 
 Subsurface::~Subsurface() noexcept {
-	wl_list_remove(&listeners.map.link);
 	wl_list_remove(&listeners.destroy.link);
 }
 

src/surface/subsurface.hpp

@@ -17,7 +17,6 @@ class Subsurface final : public Surface {
   public:
 	struct Listeners {
 		std::reference_wrapper<Subsurface> parent;
-		wl_listener map = {};
 		wl_listener destroy = {};
 		explicit Listeners(Subsurface& parent) noexcept : parent(parent) {}
 	};