#1622 Close viewer's session when mouse down

[paul Terray]

X11vnc server closes viewer's session when "mouse down" on specific situations (generaly selecting an object, eg an attachment to a mail). Once session is re-establised, th mouse down is effective and we have the expected effect (eg the attachment opens..). Happens very often, but not easy to solve or reproduce (Client version win7 serv pack 1 2009=2.7.10, Server version Lubuntu18= X11vnc 0.9.13)
Thanks for help. Paulo