Build fails if empty collections folder is referenced by pageview manager

[PeterMedina]

System Information

PHP Version:

7.4.1

stakx Version:

v0.2.0-beta1-19-g719042b

Operating System

macOS 10.15.2

Expected behavior

I expected to:

• Define collections in _config.yml
• Create blank collections folders in anticipation of future content
• Create templates for pageview manager that reference collections
• Build site

Actual behavior

Stakx will give a the following error when attempting to build:
Your website failed to build with the following error: The 'collection-name' collection is not defined

Steps to reproduce behavior

1. Define two collections: red and blue
2. Create a pageview for red and blue
3. Create a collection directory for red only and add red.md to it
4. Attempt to build site

You should receive the following error:
Your website failed to build with the following error: The 'blue' collection is not defined