Added config options. However, there is a bug. Can you help?

I wanted to quickly roll out a Vagrant Box locally and after adding some config changes, I got the following error when doing a ```vagrant up```.

```
There was an error loading a Vagrantfile. The file being loaded
and the error message are shown below. This is usually caused by
a syntax error.

Path: /Users/tarei-air/personal-projects/ourmarae/Vagrantfile
Message: undefined method `+@' for nil:NilClass
```

Got any ideas on fixes for this?