Lokijs: Inserting document with unique key violation

I am running the latest, as of 5.3.2016, minified Lokijs from Lokijs.org and NW.js v0.12.3-win-x64. I have a document already saved in Lokijs:

"collections":[{"name":"admins","data":[{"username":"erik","meta":{"revision":1,"created":1459028934981,"version":0,"updated":1462333795190},"$loki":1}],"idIndex":[1],"binaryIndices":{},"constraints":null,"uniqueNames":["username"],"transforms":{},"objType":"admins","dirty":true,"cachedIndex":null,"cachedBinaryIndex":null,"cachedData":null,"transactional":false,"cloneObjects":false,"cloneMethod":"parse-stringify","asyncListeners":false,"disableChangesApi":true,"autoupdate":false,"ttl":{"age":null,"ttlInterval":null,"daemon":null},"maxId":2,"DynamicViews":[],"events":{"insert":[null],"update":[null],"pre-insert":[],"pre-update":[],"close":[],"flushbuffer":[],"error":[null],"delete":[null],"warning":[null]},"changes":[],"username":{"name":"username","regExp":{}}}.

I am trying to generate an error when I attempt to insert a duplicate key value. I have added a unique constraint on the 'username' key in this collection and have verified the collection.uniqueNames array contains 'username'.

When I run the code below, as expected, no additional documents are inserted into the collection.data array and the database is saved. However, no errors are generated. Also, when I console.log the document object after the insert method has run, it changes to:

Object {username: "erik", meta: Object, $loki: 2}.

When I change the key value to something else, the unique document is then inserted and saved properly.

How do I go about generating an error when attempting to insert a document containing key(s) that violate unique constraints? Thank you.

insertDocument: function(objParameters) {

    var collection = objParameters.insert.collection;
    collection.ensureUniqueIndex('username');
    var document = {username: ''};
    document.username = 'erik';

    collection.on('error', function(err) {
        return console.log(err);
    });

    collection.insert(document);

    return thisModule.$body.triggerHandler('app.database.save');
}

EDIT: loki.db to test clone

{"filename":"loki.db","collections":[{"name":"test","data":[{"name":"erik","meta":{"revision":0,"created":1462493328062,"version":0},"$loki":1}],"idIndex":[1],"binaryIndices":{},"constraints":null,"uniqueNames":["name"],"transforms":{},"objType":"test","dirty":true,"cachedIndex":null,"cachedBinaryIndex":null,"cachedData":null,"transactional":false,"cloneObjects":true,"cloneMethod":"parse-stringify","asyncListeners":false,"disableChangesApi":true,"autoupdate":false,"ttl":{"age":null,"ttlInterval":null,"daemon":null},"maxId":2,"DynamicViews":[],"events":{"insert":[null],"update":[null],"pre-insert":[],"pre-update":[],"close":[],"flushbuffer":[],"error":[null],"delete":[null],"warning":[null]},"changes":[]}],"databaseVersion":1.1,"engineVersion":1.1,"autosave":false,"autosaveInterval":5000,"autosaveHandle":null,"options":{},"persistenceMethod":"fs","persistenceAdapter":null,"verbose":false,"events":{"init":[null],"loaded":[],"flushChanges":[],"close":[],"changes":[],"warning":[]},"ENV":"NODEJS"}

Code to test clone:

var loki = require('lokijs-1.3.min.js');
var db = new loki();
var collection = db.addCollection('test', {
    clone: true,
    unique: 'name'
});

collection.on('error', function(error) {
    return console.log(error);
});

collection.insert({ name: 'erik'});
collection.insert({ name: 'erik'});

db.saveDatabase();

If you don't use clone: true then you need to call coll.update(document) to force index recomputation, which will trigger the error.