The ubiquity installer for Kubuntu can be easily crashed in manual partition selecting

Started an install an selected manual partitioning.

Added sda1 as /boot
Added sda5 as /
Then realized I'd forgotten to mark sda1 as "Format" so clicked on its box.
Crash....

=====
Traceback (most recent call last).
File "/usr/lib/ubiquity/ubiquity/frontend/kde_components/PartitionModel.py", line 66 in setData
item.partman_column_format_toggled(value.toBool())
AtributeError: 'int' object has no attribute 'toBool'
=====

Looking at the error message (and code) I suspect you just need to click on the "Format" radio button.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity (not installed)
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CurrentDesktop: KDE
Date: Thu May 10 13:52:06 2018
InstallCmdLine: file=/cdrom/preseed/kubuntu.seed boot=casper maybe-ubiquity initrd=/casper/initrd.lz quiet splash --- maybe-ubiquity
InstallationDate: Installed on 2018-05-09 (0 days ago)
InstallationMedia: Kubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
SourcePackage: ubiquity
UpgradeStatus: No upgrade log present (probably fresh install)