#fixed code
                                public GraphEdge<V,E> connect(V v1, V v2, E value){
        // Check non-null arguments
        if(v1 == null || v2 == null) throw new IllegalArgumentException("Vertices cannot be null");
        // Ensure that the vertices are in the graph
        add(v1);
        add(v2);
        GraphEdge<V,E> edge = new GraphEdge<V, E>(v1, v2, value);
        GraphEdge<V,E> reversedEdge = new GraphEdge<V, E>(v2, v1, value);
        // Add edges to the graph
        connected.get(v1).add(edge);
        connected.get(v2).add(reversedEdge);
        return edge;
    }
#vulnerable code 
                                public GraphEdge<V,E> connect(V v1, V v2, E value){
        //check input
        if(v1 == null || v2 == null) throw new IllegalArgumentException("Vertices cannot be null");
        GraphEdge<V,E> edge = new GraphEdge<V, E>(v1, v2, value);
        GraphEdge<V,E> edgeReverse = new GraphEdge<V, E>(v2, v1, value);
        //add edges to the graph (if not present before)
        connected.get(v1).add(edge);
        connected.get(v2).add(edgeReverse);
        return edge;
    } 
                            #location 8 
                            #vulnerability type NULL_DEREFERENCE