Describe the issue
Creating an empty playlist throws an IndexError.

Code snippets

# The relevant code from plexapi.playlist addItems method:
# line 95
uuid = items[0].section().uuid # IndexError thrown here, there is no check for empty list.

Expected behavior
The method should either be a no-op or throw a more meaningful error (e.g. asserting the input is a non-empty List/Tuple).

Enviroment (please complete the following information):

• OS: MacOS Catalina
• Plex version 1.20.1.3252
• Python Version 3.8
• PlexAPI version 4.1.0

Stumbled across this when someone opened an issue about it on my iTunes playlist importer.