Check pkg before trying to read name.

When trying to start a new project on a empty dir, `init` will fail, the reason is that `project` is a NULL_PROJECT which doesn't have pkg https://github.com/stefanpenner/ember-cli/blob/3e9323266e4b0922d8e519a1ac5444d796c2c98a/lib/models/project.js#L30

## Steps to reproduce
```
mkdir /tmp/foo
cd /tmp/foo
ember init
```