Not quite, just got a crash:
Error while running event markers::on_gui_click (ID 1)
__markers__/control.lua:75: attempt to index field 'markers_gui' (a nil value)
stack traceback:
__markers__/control.lua:75: in function 'gui_toggle'
__markers__/control.lua:222: in function <__markers__/control.lua:219>