odf: to solve my problem, it was sufficient to adjust your code like that (the other code from the other thread wasn't really necessary):

        nr_tpolys = sum([len(actor.Geometry().TexPolygons())
                         for actor in actors if actor.Geometry().TexPolygons()])

This prop just returns 'None' for TexPolygons() (and 0 for the NumTex... methods).