R bakelet fails to install if *no packages* are provided.

[chrisparnin]

Describe the bug

R bakelet fails to install if no packages are provided.

The following error occurs.

VM is currently in state "running"
✔ Running apt-get update on VM
✔ Preparing python
✔ Installing python
✖ Preparing R
==> Error: TypeError: Cannot read property 'length' of undefined

To Reproduce

Given, the following baker.yml:

name: Rplayground
vm:
   ip: 10.50.50.50
   memory: 2048
lang:
  - python2
  - R

Expected behavior
Be able to run without requiring packages.
Adding a packages object resolves error:

  - R:
      packages: coin

Please complete the following information:
MacOS

[chrisparnin]

Looks like fix addresses this issue.