Hello!

've got segv (11) on USB-flash connection. I suppose, this situation was, when Thunar tried to get USB-flash at the same time with VBox VM. Anyway, seems to be better to show some alert-window instead of segfaulting.

[1] k_mikhail@linux-mk500:~> coredumpctl 
TIME                            PID   UID   GID SIG PRESENT EXE
Вто 2017-08-22 16:41:43 EEST   1813  1000   100  11 * /usr/bin/thunar


[2] k_mikhail@linux-mk500:~> coredumpctl gdb 1813
           PID: 1813 (Thunar)
           UID: 1000 (k_mikhail)
           GID: 100 (users)
        Signal: 11 (SEGV)
     Timestamp: Вто 2017-08-22 16:41:09 EEST (4min 5s ago)
  Command Line: Thunar --daemon
    Executable: /usr/bin/thunar
 Control Group: /user.slice/user-1000.slice/session-2.scope
          Unit: session-2.scope
         Slice: user-1000.slice
       Session: 2
     Owner UID: 1000 (k_mikhail)
       Boot ID: f5361994459f458c9a3b0174071a16c3
    Machine ID: 4664bc7cba6aee90fe1efc7f571cbf28
      Hostname: linux-mk500
      Coredump: /var/lib/systemd/coredump/core.Thunar.1000.f5361994459f458c9a3b0174071a16c3.1813.1503409269000000.xz
       Message: Process 1813 (Thunar) of user 1000 dumped core.

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Reading symbols from /usr/bin/thunar...Reading symbols from /usr/lib/debug/usr/bin/thunar.debug...done.
done.

warning: core file may not match specified executable file.
[New LWP 1813]
[New LWP 3057]
[New LWP 3061]
[New LWP 4900]
[New LWP 3058]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
Core was generated by `Thunar --daemon'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  g_type_check_instance (type_instance=type_instance@entry=0x400000000)
    at gtype.c:4137
4137	      if (type_instance->g_class)
[Current thread is 1 (Thread 0x7fde851cda00 (LWP 1813))]

[3] BackTrace:
==============
(gdb) bt
#0  0x00007fde8208005d in g_type_check_instance (type_instance=type_instance@entry=0x400000000) at gtype.c:4137
#1  0x00007fde82075cb4 in g_signal_handlers_disconnect_matched (instance=0x400000000, mask=mask@entry=G_SIGNAL_MATCH_DATA, signal_id=signal_id@entry=0, detail=detail@entry=0, closure=closure@entry=0x0, func=func@entry=0x0, data=data@entry=0x2c628c0) at gsignal.c:2925
#2  0x000000000043c29d in thunar_folder_finished (job=<optimized out>, folder=0x2c628c0 [void]) at thunar-folder.c:570
#6  0x00007fde82077592 in <emit signal ??? on instance 0x2bed650 [ThunarSimpleJob]> (instance=instance@entry=0x2bed650, signal_id=<optimized out>, detail=detail@entry=0) at gsignal.c:3441
    #3  0x00007fde8205d908 in g_closure_invoke (closure=0x2b8b510, return_value=return_value@entry=0x0, n_param_values=1, param_values=param_values@entry=0x7ffd105658b0, invocation_hint=invocation_hint@entry=0x7ffd10565850)
    at gclosure.c:804
    #4  0x00007fde8206f30d in signal_emit_unlocked_R (node=node@entry=0x29e4f90, detail=detail@entry=0, instance=instance@entry=0x2bed650, emission_return=emission_return@entry=0x0, instance_and_params=instance_and_params@entry=0x7ffd105658b0) at gsignal.c:3629
    #5  0x00007fde820772a8 in g_signal_emit_valist (instance=<optimized out>, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7ffd10565a38) at gsignal.c:3385
#7  0x00007fde84bd6171 in exo_job_async_ready (job=0x2bed650 [ThunarSimpleJob]) at exo-job.c:442
#8  0x00007fde84bd6171 in exo_job_async_ready (user_data=<optimized out>)
    at exo-job.c:281
#9  0x00007fde81d89015 in g_main_context_dispatch (context=0x24ff580)
    at gmain.c:3154
#10 0x00007fde81d89015 in g_main_context_dispatch (context=context@entry=0x24ff580) at gmain.c:3769
#11 0x00007fde81d89388 in g_main_context_iterate (context=0x24ff580, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at gmain.c:3840
#12 0x00007fde81d8964a in g_main_loop_run (loop=0x258ebe0) at gmain.c:4034
#13 0x00007fde83c557b7 in IA__gtk_main () at gtkmain.c:1268
#14 0x00000000004224ad in main (argc=1, argv=0x7ffd10565dd8) at main.c:312
(gdb) 
==============

OS: openSUSE 42.2
XFCE: 4.12
Thunar: 1.6.10