assume default 'highlight' language is 'text': just making sure we always pass a non-empty language string to highlight.js. Then our highlight.js clone can take care of the b0rkb0rkb0rk in there as per https://github.com/GerHobbelt/highlight.js/commit/9d38cfd2a75dae77f475c7b83648cd3c0f0888c3