Check whether StatusNotifierItem can Activate
Check whether StatusNotifierItem can Activate

Ayatana indicators don't follow the StatusNotifier specification and so
do not have an Activate method. This results in an error message when
the icon is clicked.

This PR checks whether the method is available before trying to call it.

Fixes: https://github.com/elParaguayo/qtile-extras/issues/130

qtile/qtile,qtile/qtile