That event comes from the toplevel and not the surface, so would cause
a use-after-free on destroy if the toplevel got destroyed first:
==5454==ERROR: AddressSanitizer: heap-use-after-free on address 0x6110001ed198 at pc 0x000000472d10 bp 0x7ffc19070a80 sp 0x7ffc19070a70
WRITE of size 8 at 0x6110001ed198 thread T0
#0 0x472d0f in wl_list_remove ../common/list.c:157
#1 0x42e159 in handle_destroy ../sway/desktop/xdg_shell_v6.c:243
#2 0x7fa9e5b28ce8 in wlr_signal_emit_safe ../util/signal.c:29
#3 0x7fa9e5afd6b1 in destroy_xdg_surface_v6 ../types/xdg_shell_v6/wlr_xdg_surface_v6.c:101
#4 0x7fa9e5d98025 in destroy_resource src/wayland-server.c:688
#5 0x7fa9e5d98091 in wl_resource_destroy src/wayland-server.c:705
#6 0x7fa9e27f103d in ffi_call_unix64 (/lib64/libffi.so.6+0x603d)
#7 0x7fa9e27f09fe in ffi_call (/lib64/libffi.so.6+0x59fe)
#8 0x7fa9e5d9bf2c (/lib64/libwayland-server.so.0+0xbf2c)
#9 0x7fa9e5d983de in wl_client_connection_data src/wayland-server.c:420
#10 0x7fa9e5d99f01 in wl_event_loop_dispatch src/event-loop.c:641
#11 0x7fa9e5d98601 in wl_display_run src/wayland-server.c:1260
#12 0x40a2f4 in main ../sway/main.c:433
#13 0x7fa9e527318a in __libc_start_main ../csu/libc-start.c:308
#14 0x40b749 in _start (/opt/wayland/bin/sway+0x40b749)
0x6110001ed198 is located 152 bytes inside of 240-byte region [0x6110001ed100,0x6110001ed1f0)
freed by thread T0 here:
#0 0x7fa9e7c89880 in __interceptor_free (/lib64/libasan.so.5+0xee880)
#1 0x7fa9e5affce9 in destroy_xdg_toplevel_v6 ../types/xdg_shell_v6/wlr_xdg_toplevel_v6.c:23
#2 0x7fa9e5d98025 in destroy_resource src/wayland-server.c:688
previously allocated by thread T0 here:
#0 0x7fa9e7c89e50 in calloc (/lib64/libasan.so.5+0xeee50)
#1 0x7fa9e5b00eea in create_xdg_toplevel_v6 ../types/xdg_shell_v6/wlr_xdg_toplevel_v6.c:427
#2 0x7fa9e27f103d in ffi_call_unix64 (/lib64/libffi.so.6+0x603d)
The toplevel only notifies the compositor on destroy if it was mapped,
so only listen to events at map time.