asserts for accessing deleted object list nodes.

src/slic3r/GUI/wxExtensions.cpp

@@ -496,6 +496,15 @@ ObjectDataViewModelNode::ObjectDataViewModelNode(ObjectDataViewModelNode* parent
     set_action_icon();
 }
 
+#ifndef NDEBUG
+bool ObjectDataViewModelNode::valid()
+{
+	// Verify that the object was not deleted yet.
+	assert(m_idx >= -1);
+	return m_idx >= -1;
+}
+#endif /* NDEBUG */
+
 void ObjectDataViewModelNode::set_action_icon()
 {
     m_action_icon_name = m_type & itObject              ? "advanced_plus" : 
@@ -1417,6 +1426,7 @@ wxDataViewItem ObjectDataViewModel::GetParent(const wxDataViewItem &item) const
 		return wxDataViewItem(0);
 
 	ObjectDataViewModelNode *node = (ObjectDataViewModelNode*)item.GetID();
+	assert(node != nullptr && node->valid());
 
 	// objects nodes has no parent too
     if (node->m_type == itObject)

src/slic3r/GUI/wxExtensions.hpp

@@ -158,7 +158,7 @@ DECLARE_VARIANT_OBJECT(DataViewBitmapText)
 
 
 // ----------------------------------------------------------------------------
-// ObjectDataViewModelNode: a node inside PrusaObjectDataViewModel
+// ObjectDataViewModelNode: a node inside ObjectDataViewModel
 // ----------------------------------------------------------------------------
 
 enum ItemType {
@@ -251,6 +251,10 @@ public:
 			ObjectDataViewModelNode *child = m_children[i];
 			delete child;
 		}
+#ifndef NDEBUG
+		// Indicate that the object was deleted.
+		m_idx = -2;
+#endif /* NDEBUG */
 	}
 
 	bool IsContainer() const
@@ -260,6 +264,7 @@ public:
 
 	ObjectDataViewModelNode* GetParent()
 	{
+		assert(m_parent == nullptr || m_parent->valid());
 		return m_parent;
 	}
 	MyObjectTreeModelNodePtrArray& GetChildren()
@@ -346,6 +351,11 @@ public:
 	bool        update_settings_digest(const std::vector<std::string>& categories);
     int         volume_type() const { return int(m_volume_type); }
     void        msw_rescale();
+
+#ifndef NDEBUG
+	bool 		valid();
+#endif /* NDEBUG */
+
 private:
     friend class ObjectDataViewModel;
 };