treeview : fix possible error
treeview : fix possible error

Node destruction on event for instance

Heigvd/Wegas,Heigvd/Wegas,ghiringh/Wegas,Heigvd/Wegas,ghiringh/Wegas,Heigvd/Wegas,ghiringh/Wegas,Heigvd/Wegas