[1.2.4] Leveling bug with Stone Alchemy (+ stonewarden?)

[twas Brillig]

Leveling a stonewarden with Stone Alchemy unlocked, with 4/3/0/1 points due to an alchemist escort. I temporarily put a point into Stone Fortress (1->2), only to find I can't take it out. Trying to remove the point brings up a pop-up:

[quote=Impossible]
You cannot unlearn this talent because of the talent(s):
-Stone Touch(not enough talents of this type known)
[/quote]

I tried to unlevel my generic for that level to put it into stone portal (and hopefully put my class talent somewhere more useful), but I get the same error.