what is the solution to the following?
Unpacking virtualmin-lamp-stack (6.0.10+deb-9) over (6.0.9+deb-9) …
Preparing to unpack …/38-milter-greylist_4.5.11-1.1+b1_amd64.deb …
Adding group greylist…done
Adding system user greylist…done
usermod: group ‘greylist’ does not exist
dpkg: error processing archive /tmp/apt-dpkg-install-rA9xIZ/38-milter-greylist_4.5.11-1.1+b1_amd64.deb (–unpack):
subprocess new pre-installation script returned error exit status 6
Errors were encountered while processing:
/tmp/apt-dpkg-install-rA9xIZ/38-milter-greylist_4.5.11-1.1+b1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)