output: #fixed code
                                  @Test
      public void testCreatorGetterObjectIdAnnotated() throws Exception {
          CreatorGetterObjectIdAnnotated o = new CreatorGetterObjectIdAnnotated(new org.bson.types.ObjectId().toString());
          JacksonDBCollection<CreatorGetterObjectIdAnnotated, String> coll = createCollFor(o, String.class);
          coll.insert(o);
          CreatorGetterObjectIdAnnotated result = coll.findOneById(o.id);
          assertThat(result, notNullValue());
          assertThat(result.getId(), equalTo(o.id));
      }
input: #vulnerable code 
                                  @Test
      public void testCreatorGetterObjectIdAnnotated() throws Exception {
          CreatorGetterObjectIdAnnotated o = new CreatorGetterObjectIdAnnotated(null);
          JacksonDBCollection<CreatorGetterObjectIdAnnotated, String> coll = createCollFor(o, String.class);
          WriteResult<CreatorGetterObjectIdAnnotated, String> writeResult = coll.insert(o);
          assertThat(writeResult.getSavedId(), notNullValue());
          assertThat(writeResult.getSavedId(), instanceOf(String.class));
          assertThat(writeResult.getDbObject().get("id"), nullValue());
          assertThat(writeResult.getSavedId(), equalTo(writeResult.getDbObject().get("_id").toString()));
          CreatorGetterObjectIdAnnotated result = coll.findOneById(writeResult.getSavedId());
          assertThat(result, notNullValue());
          assertThat(result.getId(), equalTo(writeResult.getSavedId()));
      } 
                              #location 12 
                              #vulnerability type NULL_DEREFERENCE