Fix issue with empty profile.yml file

[aaronchantrill]

Description

When using yaml.safe_load() on an empty text file, the returned value is None rather than an empty dictionary as I expected. This caused an error when adding the first value, as I would get the error message "NoneType object does not support item assignment".

This patch changes a None value into an empty dictionary.

Related Issue

NoneType does not support item assignment #413

How Has This Been Tested?

flake8 and unit tests. I also tried running Naomi with an empty profile.yml file and it worked after applying this patch.

Screenshots (if appropriate):

Types of changes

• [X] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [X] My code follows the code style of this project.
• [ ] My change requires a change to the documentation.
• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes.
• [X] All new and existing tests passed.