Throws error with `locale` option but without `supportedLocales`.

[mwistrand]

Bug

When running dojo build with a locale option but without a supportedLocales array, the build fails with an error: Path must be a string. Received undefined.

Package Version: v2.0.0-beta1.3

Code

Clone @dojo/examples and $ cd into todo-mvc-kitchensink. Remove the supportedLocales option in .dojorc (see below), and then execute $ dojo build in the command line.

{
    "build-webpack": {
        "locale": "en",
        "messageBundles": [ "src/nls/common" ]
    }
}

Expected behavior:

The build should complete with the English messages included.

Actual behavior:

An error is thrown: Path must be a string. Received undefined.