grub installation crashed during the Ubuntu 18.04 installation

[asta]

I had windows vista and Kubuntu 16.04 on my "HP pro3300 series mt" and wanted to change kubuntu with ubuntu 18.04 but the installation stopped during the Grub installation

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
CurrentDesktop: ubuntu:GNOME
Date: Fri May 4 09:30:54 2018
InstallCmdLine: BOOT_IMAGE=(loop)/casper/vmlinuz root=UUID=C2AC-5FC2 maybe-ubiquity debian-installer/language=fr keyboard-configuration/layoutcode=fr keyboard-configuration/variantcode=latin9 iso-scan/filename=/ubuntu-18.04-desktop-amd64.iso boot=casper file=/cdrom/preseed/ubuntu.seed noprompt quiet splash --
LiveMediaBuild: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
ProcEnviron:
 LANGUAGE=fr_FR.UTF-8
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=fr_FR.UTF-8
 LC_NUMERIC=C.UTF-8
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)