Remove edge leaves graph object in an inconsistent state segfault

[arcturusannamalai]

Describe the bug
Remove edge is causing a segfault because of empty iterator for erase when unwrapping a optional

To Reproduce
Write a weighted directed graph and delete the few edges after running any path finding algorithm

Additional context
On Linux machine

[ZigRazor]

@arcturusannamalai can you add a test case that give the error? Thank you in advance