Problem with Save/Load Functionality: Invalid Edges and Node Consistency

[Martinfx]

Hi,
I have a problem with the graph.hpp. Do you have some advice how to fix? Martinfx/materialeditor@0701030
There are critical issues with the current implementation of the Save and Load functionality in the project. Specifically, invalid edges and missing nodes are causing crashes and inconsistencies. Below is a detailed summary of the problem:

Problem Description:

• Invalid Edges:
  When loading a saved project, edges reference nodes that do not exist in the graph. This leads to crashes during operations like num_edges_from_node.

    Error Messages:

Error: Invalid edge. Missing nodes: 2 or 0
Error: Invalid edge. Missing nodes: 2 or 1
Error: Invalid edge. Missing nodes: 6 or 5
Error: Invalid edge. Missing nodes: 5 or 2

Node Deletion Inconsistency:

• When a node is deleted, associated edges are not removed properly. This results in dangling edges in the graph referencing deleted nodes.

Graph Integrity Check:

• The current implementation does not validate the graph's integrity during save or load operations. This can result in corrupted data being saved or loaded into the application.

Assertion Failures:

• During runtime, assertions fail due to missing edges or nodes. Examples:

Assertion failed: (iter != edges_from_node_.end()), function num_edges_from_node, file graph.hpp, line 248.