Multi probe window crashes if GO is clicked

[aboeckma]

• click Probes → create multi probe
• Do not change any options, just click GO
• BOOOOM

probe_combi_statistic::calc_fitness (this=(probe_combi_statistic *) 0x0, len_of_field=0)
Generation::calcFitness (this=(Generation *) 0x10619a7c0, use_genetic_algo=false, old_avg_fit=0)
ProbeValuation::evolution (this=(ProbeValuation *) 0x10619a760)
ProbeValuation::init_valuation (this=(ProbeValuation *) 0x10619a760)
MP_compute (cl_gb_main=4340374736)
AW_cb_struct::run_callback (this=(AW_cb_struct *) 0x10618dca0)
AW_window::click_handler (aw_cb_struct=(gpointer) 0x10618dca0)
_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 = 0x104a07e10\n  }\n})
ARB_main (argc=1, argv=(char **) 0x7fff5fbffa78)
main (argc=1, argv=(char **) 0x7fff5fbffa78)

[epruesse]

apparently fixed. results in proper warning.