Error: "This message is missing a required token" even when email contains the required tokens

Summary:
When "Disable check for mandatory tokens" setting for CiviMail is unchecked, the mailing wizard throws error messages about the required tokens being missing, even if the tokens are included in the HTML and text versions of the message.

Steps to reproduce:

• Go to Administer > CiviMail > CiviMail Component Settings, uncheck "Disable check for mandatory tokens" and save
• Create a new mailing
• In the HTML Format text area, enter this HTML for the message:
  Address: {domain.address}<br>Unsubscribe: {action.unsubscribeUrl}<br>Opt Out: {action.optOutUrl}
  - In the Plain-Text Format text area, enter this text for the message:
  Address: {domain.address}

  Unsubscribe:

  {action.unsubscribeUrl}

  Opt Out:

  {action.optOutUrl}
• Click "Next >>"

Expected result:

• Should proceed to step 4 (mail test screen) without any errors

Actual result:

• Get the following errors:
  Please correct the following errors in the form fields below:
  The following errors were detected in html message:
  This message is missing a required token - {domain.address}

  : Domain address - displays your organization's postal address.
  This message is missing a required token -

  {action.optOutUrl or action.unsubscribeUrl}

  : 'Unsubscribe via web page' - creates a link for recipients to unsubscribe from the specific mailing list used to send this message. Alternatively, you can include the 'Unsubscribe via email' token or one of the Opt-out tokens.