MainWindow, Config: Minor change and bug fixe for windows config.

src/View/Network/GraphWidget.py

@@ -279,6 +279,7 @@ class GraphWidget(QGraphicsView):
         self._selected_item = None
         self._selected_new_edge_src_node = None
         self._current_edge = None
+        self._current_moved_node = None
         self.tmp_line = None
 
         self.node_items = []
@@ -714,15 +715,16 @@ class GraphWidget(QGraphicsView):
         self.clicked = False
 
         if self._state == "move":
-            pos = self.mapToScene(event.pos())
-            self._undo.push(
-                SetNodePosCommand(
-                    self._current_moved_node,
-                    (pos.x(), pos.y()),
-                    (self._mouse_origin_x,
-                     self._mouse_origin_y)
+            if self._current_moved_node is not None:
+                pos = self.mapToScene(event.pos())
+                self._undo.push(
+                    SetNodePosCommand(
+                        self._current_moved_node,
+                        (pos.x(), pos.y()),
+                        (self._mouse_origin_x,
+                         self._mouse_origin_y)
+                    )
                 )
-            )
 
         self.update()
         super(GraphWidget, self).mouseReleaseEvent(event)