This is what gdb showed.

Thread 1 "shares-admin" received signal SIGSEGV, Segmentation fault.
0x00007ffff727e910 in g_type_check_instance_cast ()
   from /lib/x86_64-linux-gnu/libgobject-2.0.so.0
(gdb) bt
#0  0x00007ffff727e910 in g_type_check_instance_cast ()
    at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#1  0x000055555556245e in share_settings_dialog_run_for_iter ()
#2  0x000055555556309a in share_settings_dialog_run ()
#3  0x00007ffff7256a56 in  () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#4  0x00007ffff7275b28 in g_signal_emit_valist ()
    at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#5  0x00007ffff72760d3 in g_signal_emit ()
    at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#6  0x00007ffff793b2ae in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#7  0x00007ffff793b318 in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#8  0x00007ffff7256a56 in  () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#9  0x00007ffff7275b28 in g_signal_emit_valist ()
    at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#10 0x00007ffff72760d3 in g_signal_emit ()
    at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#11 0x00007ffff7939754 in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#12 0x00007ffff7beaa71 in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#13 0x00007ffff7256a56 in  () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#14 0x00007ffff7275b28 in g_signal_emit_valist ()
    at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#15 0x00007ffff72760d3 in g_signal_emit ()
    at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#16 0x00007ffff7a01f5c in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#17 0x00007ffff7259c56 in g_cclosure_marshal_VOID__BOXEDv () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#18 0x00007ffff7256a56 in  () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#19 0x00007ffff7275b28 in g_signal_emit_valist () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#20 0x00007ffff72760d3 in g_signal_emit () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#21 0x00007ffff79fefa2 in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#22 0x00007ffff7a005eb in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#23 0x00007ffff7a035d6 in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#24 0x00007ffff79cabb0 in gtk_event_controller_handle_event () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#25 0x00007ffff7b8d0fd in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#26 0x00007ffff7be457f in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#27 0x00007ffff7256a56 in  () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#28 0x00007ffff7274dd1 in g_signal_emit_valist () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#29 0x00007ffff72760d3 in g_signal_emit () at /lib/x86_64-linux-gnu/libgobject-2.0.so.0
#30 0x00007ffff7b8ebb3 in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#31 0x00007ffff7a4a0b8 in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#32 0x00007ffff7a4c36b in gtk_main_do_event () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#33 0x00007ffff7734f79 in  () at /lib/x86_64-linux-gnu/libgdk-3.so.0
#34 0x00007ffff7768106 in  () at /lib/x86_64-linux-gnu/libgdk-3.so.0
#35 0x00007ffff716afbd in g_main_context_dispatch () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#36 0x00007ffff716b240 in  () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#37 0x00007ffff716b533 in g_main_loop_run () at /lib/x86_64-linux-gnu/libglib-2.0.so.0
#38 0x00007ffff7a4b30d in gtk_main () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#39 0x000055555555fc9d in main ()