Network: Fix 'previous_item' c++ object deleted.

src/View/Network/GraphWidget.py

@@ -17,6 +17,7 @@
 # -*- coding: utf-8 -*-
 
 import math
+import logging
 
 from tools import timer
 
@@ -39,6 +40,8 @@ from Model.Network.Graph import Graph
 
 from View.Network.UndoCommand import *
 
+logger = logging.getLogger()
+
 _translate = QCoreApplication.translate
 
 
@@ -571,14 +574,17 @@ class GraphWidget(QGraphicsView):
         Returns:
             Nothing
         """
-        previous_item = self._selected_item
-        self._selected_item = item
+        try:
+            previous_item = self._selected_item
+            self._selected_item = item
 
-        if previous_item:
-            previous_item.update()
+            if previous_item:
+                previous_item.update()
 
-        if item:
-            item.update()
+                if item:
+                    item.update()
+        except Exception as e:
+            logger.debug(str(e))
 
     def selected_new_edge_src_node(self):
         """The current node item selected to add new edge