Xubuntu installer crashed

[John Shakespeare]

Xubuntu installer crashed. This is on a Lenovo P50S system, where the "Something else" option was selected. Gparted had already been used to prepare a partition.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63.3
ProcVersionSignature: Ubuntu 4.4.0-46.67-generic 4.4.24
Uname: Linux 4.4.0-46-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CasperVersion: 1.376.2
Date: Tue Dec 13 16:58:42 2016
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi file=/cdrom/preseed/xubuntu.seed boot=casper quiet splash ---
LiveMediaBuild: Xubuntu 16.04.1 LTS "Xenial Xerus" - Beta amd64 (20161106)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)