LiteCoreException Invalid data

In side a query change listener I have written following Code

@Override
public void changed(QueryChange event) {
    ObjectMapper objectMapper = new ObjectMapper();
    objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
    for (Result result : event.getResults()) {
    listFromEnum.add(objectMapper.convertValue(result.toMap(), ContactPojo.class));
  }

but I am getting following error inside toMap() on result.

07-28 14:04:59.415 4115-4233/com.diro E/dirocrash: LiteCoreException{domain=4, code=3, msg=invalid data}
java.lang.Error: LiteCoreException{domain=4, code=3, msg=invalid data}
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1119)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)
Caused by: LiteCoreException{domain=4, code=3, msg=invalid data}
at com.couchbase.litecore.fleece.FLDict.getKeyString(Native Method)
at com.couchbase.litecore.fleece.FLDict.getKeyString(FLDict.java:43)
at com.couchbase.litecore.SharedKeys.getKey(SharedKeys.java:78)
at com.couchbase.litecore.SharedKeys.getDictIterKey(SharedKeys.java:65)
at com.couchbase.litecore.SharedKeys.getKey(SharedKeys.java:99)
at com.couchbase.litecore.fleece.FLValue.toObject(FLValue.java:221)
at com.couchbase.litecore.SharedKeys.valueToObject(SharedKeys.java:56)
at com.couchbase.litecore.SharedKeys.getDictIterKey(SharedKeys.java:67)
at com.couchbase.litecore.SharedKeys.getKey(SharedKeys.java:99)
at com.couchbase.litecore.fleece.FLValue.toObject(FLValue.java:221)
at com.couchbase.litecore.SharedKeys.valueToObject(SharedKeys.java:56)
at com.couchbase.litecore.SharedKeys.valueToObject(SharedKeys.java:93)
at com.couchbase.lite.Result.toList(Result.java:244)
at com.couchbase.lite.Result.toMap(Result.java:426)
at com.diro.linking.view.contactlistview.ContactListActivity.changed(ContactListActivity.java:1202)
at com.couchbase.lite.QueryChangeListenerToken$1.run(QueryChangeListenerToken.java:37)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1113)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:588)
at java.lang.Thread.run(Thread.java:818)