fix: cmd_sticky crash sway with empty container

[mek-yt]

When I used my sticky shortcut on an empty workspace (mouse pointer over wallpaper), sway crash with stack trace:

Stack trace of thread 11312:
#0  0x000055e2f1e07b20 container_is_floating (sway)
#1  0x000055e2f1dfd67d cmd_sticky (sway)
#2  0x000055e2f1dcd63a execute_command (sway)
#3  0x000055e2f1df255d seat_execute_command (sway)
#4  0x000055e2f1dedab7 handle_keyboard_key (sway)
#5  0x00007feee8f021c5 wlr_signal_emit_safe (libwlroots.so.0)
#6  0x00007feee8eec544 wlr_keyboard_notify_key (libwlroots.so.0)
#7  0x00007feee8ec131c handle_keyboard_key (libwlroots.so.0)
#8  0x00007feee8ec0f56 handle_libinput_event (libwlroots.so.0)
#9  0x00007feee8ebfe88 handle_libinput_readable (libwlroots.so.0)
#10 0x00007feee8f40702 wl_event_loop_dispatch (libwayland-server.so.0)
#11 0x00007feee8f3f2ac wl_display_run (libwayland-server.so.0)
#12 0x000055e2f1dd97c5 server_run (sway)
#13 0x000055e2f1dd8eda main (sway)
#14 0x00007feee8a70223 __libc_start_main (libc.so.6)
#15 0x000055e2f1dccb2e _start (sway)

Stack trace of thread 11314:
#0  0x00007feee8a38afc pthread_cond_wait@@GLIBC_2.3.2 (libpthread.so.0)
#1  0x00007feee4d5d17c n/a (i965_dri.so)
#2  0x00007feee4d5ceb8 n/a (i965_dri.so)
#3  0x00007feee8a32a9d start_thread (libpthread.so.0)
#4  0x00007feee8b47a43 __clone (libc.so.6)

Checking if the container is null solve this.
But this fix will mislead the cmd_sticky to think that the container is a tiled container.

If this is a bug, do you prefer testing if the container is null in cmd_sticky function ?

[ianyfan]

This isn't the right check. The right check is that the container isn't NULL in cmd_sticky, like in #2794

[RyanDwyer]

Thanks!