Cope with unset history in midori_location_action_toggle_arrow_cb
Cope with unset history in midori_location_action_toggle_arrow_cb

If history is unset, we don't have any items to populate the
combobox dropdown with. So we should always hide the button. Also
suppress the popup if we have no history.

OoberMick/Midori,OoberMick/Midori