ensure that there are no duplicate names in lists; disable cp/rm actions for empty lists

GUI/View/List/DatafilesSelector.cpp

@@ -56,6 +56,7 @@ DatafilesSelector::DatafilesSelector()
     splitter->addWidget(m_editor);
     splitter->setChildrenCollapsible(true);
 
+    connect(m_set, &AbstractSetModel::setChanged, this, &DatafilesSelector::updateActions);
     updateActions();
 }