[1.01] I can build multiple unique improvement, even if I'm short on cash to do so

I'm currently at -24 gilden for having built... Well, I'm not sure what I was building, because the alt-tab just crashed the game . Maybe the study. You'll have guessed I had only 1 gilden left to start the job...

It happened as the town was building something it is supposed to have only one, (maybe the merchant). I was still being proposed to build it... I had this bug multiple times before; I'm amazed to be the first to see it...