Ah, fair enough, and thank you for the response. 
I looked through my version of DirectDialog.py, and found two places in which getTightBounds was being used; I’ve altered both such that, when “bounds” is None, the values derived (left, right, top and bottom values, I believe) from it are all set to zero. I don’t know whether this might cause further issues later on (I doubt it, since this was presumably the result when getTightBounds returned (Point3(0, 0, 0), Point3(0, 0, 0))), but for now it seems to work.
Of course, I don’t know whether the issue occurs anywhere else–thus far I haven’t noticed any other problems that seem to be related to it.