fix hanging of ClosingHandler.object_button_quit_changed()
fix hanging of ClosingHandler.object_button_quit_changed()

vlukes/sfepy,sfepy/sfepy,sfepy/sfepy,vlukes/sfepy,sfepy/sfepy,rc/sfepy,vlukes/sfepy,BubuLK/sfepy,rc/sfepy,BubuLK/sfepy,BubuLK/sfepy,rc/sfepy