Installer crashed on exit

[link]

After installing Ubuntu 15.04 onto a new volume in an existing LVM, the installation finished but the installer crashed after clicking the "Continuing testing Ubuntu" button.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: ubiquity 2.21.25
ProcVersionSignature: Ubuntu 3.19.0-15.15-generic 3.19.3
Uname: Linux 3.19.0-15-generic x86_64
ApportVersion: 2.17.2-0ubuntu1
Architecture: amd64
CasperVersion: 1.360
Date: Tue Aug 11 13:35:18 2015
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz.efi initrd=/casper/initrd.lz file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash nomodeset ---
LiveMediaBuild: Ubuntu 15.04 "Vivid Vervet" - Release amd64 (20150422)
ProcEnviron:
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)