env doesn't append array values to default

nodejs version: all
nconf version: v0.11.3

Steps to Reproduce

Create an application that uses nconf with env parsing and the following defaults.

const conf = require("nconf")
    .env({
        separator: "__",
        parseValues: true,
    });

conf.defaults({
    myarray: ["value1"]
});

myarray__1=value2

The resulting array has two values.

const myarray = conf.get("myarray");
// [
//    0: 'value1',
//    1: 'value2'
// ]

The result is transformed to an object with one value, value2 with key 1. The first value of key 0 is missing and the object is not iterable.

const myarray = conf.get("myarray");
// {
//    1: 'value2'
// }