Clicking on window corner (x) should not close program,
but only hide it in the tray.
By default, after running my tunnels, I want gSTM to be
hidden in a tray. Window minimize do not solve the problem.
I know there is a context menu for gSTM icon with
command "Hide gSTM", but more intuitive operation would
be to hide gSTM window even by clicking on "close" x in
the window corner.
If somebody really wants to close gSTM - he should use