Hi, I have no idea why a package with such a serious issue has been allowed to migrate to Testing, but here's a fix anyway: get the previous version (both amd64 and i386) from snapshot.debian.org [1] and install it via dpkg.
After that, you can hold it for a while using apt-mark (preventing it from the upgrade). [1] http://snapshot.debian.org/package/nas/1.9.4-1/#libaudio2_1.9.4-1
