Similar to previously reported install crash when trying to execute grub install. I'm issuing a new bug report only because this is with version 18.04.2 LTS. Previously submitted similar bug reports were with previous versions of Ubuntu.
ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14.12
ProcVersionSignature: Ubuntu 4.18.0-15.16~18.04.1-generic 4.18.20
Uname: Linux 4.18.0-15-generic x86_64
ApportVersion: 2.20.9-0ubuntu7.5
Architecture: amd64
CasperVersion: 1.394
CurrentDesktop: ubuntu:GNOME
Date: Wed Apr 17 19:45:41 2019
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 18.04.2 LTS "Bionic Beaver" - Release amd64 (20190210)
ProcEnviron:
LANGUAGE=en_CA.UTF-8
PATH=(custom, no user)
XDG_RUNTIME_DIR=<set>
LANG=en_CA.UTF-8
LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)
Thank you for your bug report, the error is
'grub-install: error: efibootmgr failed to register the boot entry: Block device required.'
Could you describe what type of partionning you selected? Did you select manual layout? Which ones did you create with what filesystem? (could be one of those case where an EFI partition is needed but was not created which is easy to overlook when doing custom disks configuration)