Avoid zombification of processes started by clicking
Avoid zombification of processes started by clicking

Fixes bug #3896.

tonypaulic/xfce4-genmon-plugin,tonypaulic/xfce4-genmon-plugin,tonypaulic/xfce4-genmon-plugin,xfce-mirror/xfce4-genmon-plugin,xfce-mirror/xfce4-genmon-plugin,dnschneid/xfce4-genmon-plugin,xfce-mirror/xfce4-genmon-plugin,dnschneid/xfce4-genmon-plugin,dnschneid/xfce4-genmon-plugin