fix newsletter process for emails never seen

Spot-check (twice):

1. Sign in with an email you've never used before on any MDN server (e.g., '<real-email>+basket+local2@gmail.com')
2. Do **NOT** check the newsletter sign-up box
3. Should register fine
4. Edit your profile - check/un-check the newsletter box between edits and verify the page saves your state as expected

1. Sign in with an email you've never used before on any MDN server (e.g., '<real-email>+basket+local3@gmail.com')
2. **DO** check the newsletter sign-up box
3. Should register fine
4. Edit your profile - verify the newsletter box is initially checked. 
5. Check/un-check the newsletter box between edits and verify the page saves your state as expected