os installation wizard crashes after grub-efi-amd64-signed installation error

[Marco Nisato]

Release: Lubuntu 18.04.01 LTS Bionic Beaver

I expected the installation went on. After the installer told me that there was an error in installing the package "grub-efi-amd64-signed", the installer crashed.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14.6 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 4.15.0-29.31-generic 4.15.18
Uname: Linux 4.15.0-29-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.2
Architecture: amd64
CasperVersion: 1.394
Date: Fri Dec 21 21:49:21 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/lubuntu.seed boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Lubuntu 18.04.1 LTS "Bionic Beaver" - Release amd64 (20180725)
ProcEnviron:
 LANGUAGE=it_IT.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=it_IT.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)