#fixed code
                                @Test
    public void canUpsert() throws Exception {

        /* when */
        WriteResult writeResult = collection.update("{}").upsert().with("{$set:{name:'John'}}");

        /* then */
        People john = collection.findOne("{name:'John'}").as(People.class);
        assertThat(john.getName()).isEqualTo("John");
        assertThat(writeResult).isNotNull();
    }
#vulnerable code 
                                @Test
    public void canUpsert() throws Exception {

        /* when */
        WriteResult writeResult = collection.upsert("{}", "{$set:{name:'John'}}");

        /* then */
        People john = collection.findOne("{name:'John'}").as(People.class);
        assertThat(john.getName()).isEqualTo("John");
        assertThat(writeResult).isNotNull();
    } 
                            #location 9 
                            #vulnerability type NULL_DEREFERENCE