refactor(gmailEmails.py): improve Gmail email parsing and decoding logic

[Sep79]

• Added null checks for email ID (row[7]) to avoid processing null values.
• Simplified and optimized logic for extracting 'to', 'toname', 'replyto', and 'replytoname' using get method with fallbacks.
• Fixed decoding for 'mailedby' and 'signedby' by handling cases where these fields might be missing or empty.
• Ensured proper handling of message HTML content by appending decoded message parts correctly.
• Retained functionality for generating reports, timelines, and TSV files for Gmail email data, label details, and download requests.
• Updated logic for attaching files, checking for 'noname' and empty values in attachment fields.

No major changes to the database querying logic or report generation. Code adjusted for better maintainability and clarity.