"Pack Similar Tiles.lua" script ends up with a hole in the tilemap

Using this image with tile size as 16x16 and sprite sheet width of 256


The resulting tilemap has a black pixel in it, which is `0` in the png data at `(50,29)`


Here is a scaled copy of the tilemap at 4x to help show the black pixel


Third row up from bottom, about a third of the way across.

I am digging into this now and see if I can figure it out. But I figured I'd post here too in case this is known or anyone has any ideas.

If I figure it out, I'll submit a PR.

Oh and here is the tileset, in case that is helpful