Mailing fails with DB error when an emoji is pasted in to email body

User pasted a long text into the html editor in Civi mailing including a couple of emojis. CiviCRM then crashed with a DB error (traceback attached) and keeps coming up with the same error if you proceed. The traceback.txt Reproducible on 5.15.2, 5.18.2 and dmaster. The emoji in question is a smiley face