Installer crash creating a new partition table

[Ian Turner]

STEPS TO REPRODUCE:
1. Choose manually edit partition table.
2. Create a new partition with type "Physical volume for encryption".
3. Click on the raw device (/dev/sda in my case)
4. Click "New partition Table..."
5. Installer crashes.

Here is the stack trace:
Traceback (most recent call last):
  File "/usr/lib/ubiquity/ubiquity/frontend/kde_components/PartMan.py", line 441, in on_new_table_clicked
    self.ctrlr.dbfilter.create_label(devpart)
  File "/usr/lib/ubiquity/plugins/ubi-partman.py", line 3272, in create_label
    assert self.current_question == 'partman/choose_partition'
AssertionError

This is using the Kubuntu 18.04 Beta 1 ISO.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.3
ProcVersionSignature: Ubuntu 4.15.0-10.11-generic 4.15.3
Uname: Linux 4.15.0-10-generic x86_64
ApportVersion: 2.20.8-0ubuntu10
Architecture: amd64
CasperVersion: 1.389
Date: Wed Mar 21 20:23:12 2018
InstallCmdLine: file=/cdrom/preseed/kubuntu.seed boot=casper maybe-ubiquity initrd=/casper/initrd.lz quiet splash --- maybe-ubiquity
LiveMediaBuild: Kubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180306.1)
ProcEnviron:
 LANGUAGE=
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[James O'Beirne (james-obeirne)]

In my case, I encountered this error while trying to install to a disk that had a pre-existing lvm lvgroup on it. I was able to resolve the error by using gparted from the livecd to manually wipe the existing partition table. After wiping the disk, I restarted the installation process successfully.