How can I resolve the error "None should be instance of 'dict'" in panther analysis tool?

Issue

When uploading or testing via panther analysis tool, I get an error for one or more of my YAML files:

Errors:
        /Path/To/Your/YAML/File
                None should be instance of 'dict'

Resolution

Most often, this error is caused by the YAML file having no contents. Ensure that any changes you've made to the file have been saved before running panther analysis tool.

Cause

When panther analysis tool loads an empty file, it reads the whole file as a single None value. When the file has YAML content, it's interpreted as a dict object.