output: #fixed code
                                  @Test
      public void testBatchUpdatePersistentVertices() {
          Vertex v1 = this.sqlgGraph.addVertex(T.label, "Person", "name", "a");
          Vertex v2 = this.sqlgGraph.addVertex(T.label, "Person", "surname", "b");
          this.sqlgGraph.tx().commit();
          assertEquals("a", this.sqlgGraph.traversal().V(v1.id()).next().value("name"));
          assertEquals("b", this.sqlgGraph.traversal().V(v2.id()).next().value("surname"));
  
          this.sqlgGraph.tx().rollback();
          this.sqlgGraph.tx().normalBatchModeOn();
          v1.property("name", "aa");
          v2.property("surname", "bb");
          this.sqlgGraph.tx().commit();
  
          assertEquals("aa", this.sqlgGraph.traversal().V(v1.id()).next().value("name"));
          assertEquals("bb", this.sqlgGraph.traversal().V(v2.id()).next().value("surname"));
      }
input: #vulnerable code 
                                  @Test
      public void testBatchUpdatePersistentVertices() {
          Vertex v1 = this.sqlgGraph.addVertex(T.label, "Person", "name", "a");
          Vertex v2 = this.sqlgGraph.addVertex(T.label, "Person", "surname", "b");
          this.sqlgGraph.tx().commit();
          assertEquals("a", this.sqlgGraph.v(v1.id()).value("name"));
          assertEquals("b", this.sqlgGraph.v(v2.id()).value("surname"));
  
          this.sqlgGraph.tx().rollback();
          this.sqlgGraph.tx().normalBatchModeOn();
          v1.property("name", "aa");
          v2.property("surname", "bb");
          this.sqlgGraph.tx().commit();
  
          assertEquals("aa", this.sqlgGraph.v(v1.id()).value("name"));
          assertEquals("bb", this.sqlgGraph.v(v2.id()).value("surname"));
      } 
                              #location 6 
                              #vulnerability type NULL_DEREFERENCE