Junk data returned for address headers that are not used

[seanthegeek]

Describe the bug

mail-parser returns a list containing one empty tuple for delivered-to, reply-to, bcc``, and ``cc when those headers are not used.

To Reproduce

Parse the example email

Expected behavior

Headers that are not used should not be included in the output.

Raw mail

From: alice@example.com 
To: example@example.com
Subject: Example Email

Hello world!

Environment

• OS: Linux
• Docker: No
• Python version: 3.11.2
• mail-parser version 4.1.2