xdg-surface: avoid emitting signals with their owner object

https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/1008#note_1139647

types/xdg_shell/wlr_xdg_shell.c

@@ -84,7 +84,7 @@ static int xdg_client_ping_timeout(void *user_data) {
 
 	struct wlr_xdg_surface *surface;
 	wl_list_for_each(surface, &client->surfaces, link) {
-		wlr_signal_emit_safe(&surface->events.ping_timeout, surface);
+		wlr_signal_emit_safe(&surface->events.ping_timeout, NULL);
 	}
 
 	client->ping_serial = 0;

types/xdg_shell/wlr_xdg_surface.c

@@ -37,7 +37,7 @@ void unmap_xdg_surface(struct wlr_xdg_surface *surface) {
 
 	// TODO: probably need to ungrab before this event
 	if (surface->mapped) {
-		wlr_signal_emit_safe(&surface->events.unmap, surface);
+		wlr_signal_emit_safe(&surface->events.unmap, NULL);
 	}
 
 	switch (surface->role) {
@@ -312,7 +312,7 @@ void xdg_surface_role_commit(struct wlr_surface *wlr_surface) {
 	if (surface->configured && wlr_surface_has_buffer(surface->surface) &&
 			!surface->mapped) {
 		surface->mapped = true;
-		wlr_signal_emit_safe(&surface->events.map, surface);
+		wlr_signal_emit_safe(&surface->events.map, NULL);
 	}
 }
 
@@ -405,7 +405,7 @@ void reset_xdg_surface(struct wlr_xdg_surface *surface) {
 	}
 
 	if (surface->added) {
-		wlr_signal_emit_safe(&surface->events.destroy, surface);
+		wlr_signal_emit_safe(&surface->events.destroy, NULL);
 		surface->added = false;
 	}