I wrote make update for myself, some years ago, to help with syncing tex4ht dev and tl. I don't expect anyone else to be using it. I promise nothing about it, including whether it will keep existing.

Anyway, I don't see the error offhand. The line number is misleading. Have to divide and conquer the update target to see where the problem is, and I can't do that now. I'll get to it eventually, or if someone else cares and gets to it first, great.