Fixed crash on vertex_remove

graph.cpp

@@ -143,10 +143,9 @@ void Graph::remove_vertex(Vertex* target)
     for (cursor = target->neighbors.begin(); cursor != target->neighbors.end();
 	 cursor++)
     {
-	Vertex* neighbor = *cursor;
 	list<Vertex*>::iterator subcursor = find(target->neighbors.begin(),
 						 target->neighbors.end(),
-						 target);
+						 *cursor);
 	assert(subcursor != target->neighbors.end());
 	target->neighbors.erase(subcursor);
     }