ToME: the Tales of Maj'Eyal

On a farportal level 3, I got an empty 7-tiles level...
Easy to clear (!), but no boss, and no downward stair.

I tried to add an screenshot, but the file is too big.
To help the localisation of the problem, maps of previous levels were completely sandy, and rather small compared to usual farportal levels.

I've seen this as well, where levels are using the "elven ruins" style map generator (I believe), it can create very small levels.

Here is a screen shot in reduced resolution