ubuntu 18 crashed at installation alongside windows

[Florin Emanuel Lazar]

on the same drive i had, in this order, windows 10, a storage partition and an ubuntu 16 partition. the storage and ubuntu partitions were in the same extended partition. I shrincked the storage to give ubuntu more space and then tried to install the 18.04 version. At the end of the insatalation this bug occured.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14
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
CasperVersion: 1.394
Date: Sun May 6 23:41:25 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper only-ubiquity quiet splash ---
LiveMediaBuild: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)