Tree Save does not work

[aboeckma]

• click Tree → Tree Admin → Export
• Enter a random filename
• click save

provoke_core_dump ()
GBK_terminate (error=0x1003eac70 \"Selection list 'tmp/ad_tree/import_tree/filter' has no default selection\")
GBK_terminatef (templat=0x1003193a4 \"Selection list '%s' has no default selection\")
AW_selection_list::refresh (this=(AW_selection_list *) 0x104af4c00)
AW_selection_list::update (this=(AW_selection_list *) 0x104af4c00)
AW_window::update_option_menu (this=(AW_window *) 0x104af2060)
create_tree_import_window (root=(AW_root *) 0x102b15660)
AW_cb_struct::run_callback (this=(AW_cb_struct *) 0x1061093f0)
AW_window::click_handler (aw_cb_struct=(gpointer) 0x1061093f0)
_g_closure_invoke_va ()
g_signal_emit_valist ()
g_signal_emit ()
gtk_real_button_released ()
_g_closure_invoke_va ()
g_signal_emit_valist ()
g_signal_emit ()
gtk_button_button_release ()
_gtk_marshal_BOOLEAN__BOXED ()
g_closure_invoke ()
signal_emit_unlocked_R ()
g_signal_emit_valist ()
g_signal_emit ()
gtk_widget_event_internal ()
gtk_propagate_event ()
gtk_main_do_event ()
gdk_event_dispatch ()
g_main_context_dispatch ()
g_main_context_iterate ()
g_main_loop_run ()
gtk_main ()
AW_root::main_loop (this=(AW_root *) 0x102b15660)
startup_gui (cl=(NtreeCommandLine &) @0x7fff5fbff9d8: {\n  <Noncopyable> = {<No data fields>}, \n  members of NtreeCommandLine: \n  _vptr$NtreeCommandLine = 0x1003b51b8, \n  arg_count = 0, \n  args = 0x7fff5fbffa80, \n  help_requested = false, \n  do_import = false, \n  macro_name = 0x0\n}, error=(ARB_ERROR &) @0x7fff5fbff9d0: {\n  error = {\n    object = 0x103c082b0\n  }\n})
ARB_main (argc=1, argv=(char **) 0x7fff5fbffa78)
main (argc=1, argv=(char **) 0x7fff5fbffa78)