added first version of a backup system (#37)

Co-authored-by: Dominik Demuth <dominik.demuth@physik.tu-darmstadt.de>
Reviewed-on: #37

src/gui_qt/main/management.py

@@ -180,7 +180,10 @@ class UpperManagement(QtCore.QObject):
             graph.active = active
             graph.listWidget.blockSignals(True)
             for i, l in enumerate(g['in_legend']):
-                graph.listWidget.item(i).setCheckState(l)
+                try:
+                    graph.listWidget.item(i).setCheckState(QtCore.Qt.Checked if l else QtCore.Qt.Unchecked)
+                except AttributeError:
+                    pass
             graph.listWidget.blockSignals(False)
 
             #  set unchecked in tree and hide/show in plot