Operations on lists fail when the list file does not exist

[AzureMarker]

When a list file, such as whitelist.txt does not exist, the API throws an error.
This is a valid case, because some of the files are not created during the install. If they are missing they are assumed empty. The code was made to handle this, but some refactoring may have broken it.

All operations (GET, POST, DELETE) on the whitelist and blacklist have this issue. The regex list does not, because it is created during install.