Crash on unbuntu 16.04.2 install from USB to External HDD

[Jon Jet]

Was installing Ubuntu 16.04.2 from a USB Drive onto an External HDD. It crashed when installing grub installer.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63.3 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 4.8.0-36.36~16.04.1-generic 4.8.11
Uname: Linux 4.8.0-36-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.5
Architecture: amd64
CasperVersion: 1.376.2
Date: Fri Jul 14 22:13:45 2017
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash ---
LiveMediaBuild: Ubuntu 16.04.2 LTS "Xenial Xerus" - Release amd64 (20170215.2)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[apt-ghetto (apt-ghetto)]

You try to install Ubuntu in EFI mode, but you don not have an EFI-System-Partition.

If you wish to have a dualboot with Windows, please check first in which mode Windows is installed.

[Launchpad Janitor (janitor)]

[Expired for grub-installer (Ubuntu) because there has been no activity for 60 days.]