Corrigendum: Uniqueness of smooth extensions of generalized cohomology theories

The proof of Theorem 7.12 of "Uniqueness of smooth cohomology theories" by the authors of this note is not correct. The said theorem identifies the flat part of a differential extension of a generalized cohomology theory E with ER/Z (there called "smooth extension"). In this note, we give a correct proof. Moreover, we prove slightly stronger versions of some of the other results of that paper.