Fix behavior in multiple mode
Fix behavior in multiple mode

Clicking on one selected marker in a group of selected marker
should highlight only this marker.

PabloCastellano/libchamplain,PabloCastellano/libchamplain,GNOME/libchamplain,StanciuMarius/Libchamplain-map-wrapping,StanciuMarius/Libchamplain-map-wrapping,Distrotech/libchamplain,GNOME/perl-Gtk2-Champlain,Distrotech/libchamplain,Distrotech/libchamplain,GNOME/perl-Champlain,GNOME/perl-Champlain,potyl/champlain,StanciuMarius/Libchamplain-map-wrapping,StanciuMarius/Libchamplain-map-wrapping,Distrotech/libchamplain,PabloCastellano/libchamplain,potyl/champlain,potyl/champlain,PabloCastellano/libchamplain,potyl/champlain,StanciuMarius/Libchamplain-map-wrapping,Distrotech/libchamplain,GNOME/libchamplain,PabloCastellano/libchamplain,GNOME/perl-Gtk2-Champlain