add cons_exittitle_setting to tests

tests/ui/stub_ui.c

@@ -433,6 +433,7 @@ void cons_time_setting(void) {}
 void cons_mouse_setting(void) {}
 void cons_statuses_setting(void) {}
 void cons_titlebar_setting(void) {}
+void cons_exittitle_setting(void) {}
 void cons_notify_setting(void) {}
 void cons_states_setting(void) {}
 void cons_outtype_setting(void) {}