Message of thanks does not convert tokens into replacement values, outputs empty status message if left blank

Problem/Motivation

Two bugs with the new custom Message of Thanks functionality.

One, if it is left blank a Drupal message is still triggered, leading to an empty bullet point above the receipt sent status message.

Two, Give's custom tokens ([donor_name] etc) are not swapped out for corresponding values as promised by the "Tokens are allowed... " help text.