Created attachment 9687 
(gdb) t a a bt f

xfce4-session 4.14.2 (and 4.14.0) crash, when a VNC server is used and there seems to be an issue regarding the X_DISPLAY.

```
Program terminated with signal SIGSEGV, Segmentation fault.
#0  xfsm_manager_get_shutdown_type (manager=manager@entry=0x0)
    at /dev/shm/bee-root/xfce4-session/xfce4-session-4.14.2-0/source/xfce4-session/xfsm-manager.c:1931
1931	  return manager->shutdown_type;
[Current thread is 1 (Thread 0x7fbe774ef980 (LWP 4882))]
(gdb) bt
#0  0x0000000000426470 in xfsm_manager_get_shutdown_type (manager=manager@entry=0x0)
    at /dev/shm/bee-root/xfce4-session/xfce4-session-4.14.2-0/source/xfce4-session/xfsm-manager.c:1931
#1  0x0000000000419fd0 in name_lost (connection=<optimized out>, name=<optimized out>, user_data=<optimized out>)
    at /dev/shm/bee-root/xfce4-session/xfce4-session-4.14.2-0/source/xfce4-session/main.c:228
#2  0x00007fbe7dc9df06 in do_call (client=0x5fca80, call_type=CALL_TYPE_NAME_LOST) at ../source/gio/gdbusnameowning.c:215
#3  0x00007fbe7dc9e2b0 in connection_get_cb (source_object=<optimized out>, res=0x7df570, user_data=0x5fca80) at ../source/gio/gdbusnameowning.c:491
#4  0x00007fbe7dc3f5e9 in g_task_return_now (task=0x7df570 [GTask]) at ../source/gio/gtask.c:1214
#5  0x00007fbe7dc40123 in g_task_return (task=0x7df570 [GTask], type=<optimized out>) at ../source/gio/gtask.c:1283
#6  0x00007fbe7dc40bf6 in g_task_return (type=G_TASK_RETURN_ERROR, task=<optimized out>) at ../source/gio/gtask.c:1868
#7  0x00007fbe7dc40bf6 in g_task_return_error (task=<optimized out>, error=<optimized out>) at ../source/gio/gtask.c:1867
#8  0x00007fbe7dc90b30 in bus_get_async_initable_cb (source_object=0x49f5a0 [GDBusConnection], res=0x7df630, user_data=user_data@entry=0x7df570)
    at ../source/gio/gdbusconnection.c:7357
#9  0x00007fbe7dc3f5e9 in g_task_return_now (task=0x7df630 [GTask]) at ../source/gio/gtask.c:1214
#10 0x00007fbe7dc3f629 in complete_in_idle_cb (task=0x7df630) at ../source/gio/gtask.c:1228
#11 0x00007fbe7dabb404 in g_main_dispatch (context=0x49d9f0) at ../source/glib/gmain.c:3309
#12 0x00007fbe7dabb404 in g_main_context_dispatch (context=context@entry=0x49d9f0) at ../source/glib/gmain.c:3974
#13 0x00007fbe7dabb778 in g_main_context_iterate (context=0x49d9f0, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>)
    at ../source/glib/gmain.c:4047
#14 0x00007fbe7dabba32 in g_main_loop_run (loop=0x67e0c0) at ../source/glib/gmain.c:4241
#15 0x00007fbe7e96bf05 in gtk_main () at /dev/shm/bee-root/gtk3/gtk3-3.24.14-0/source/gtk/gtkmain.c:1325
#16 0x0000000000414458 in main (argc=<optimized out>, argv=<optimized out>)
    at /dev/shm/bee-root/xfce4-session/xfce4-session-4.14.2-0/source/xfce4-session/main.c:367
```

Please find the full trace attached.