installer crashes before installin grub

[Ojaswni Gujarathi]

while i am dual booting it says that no other os is detected and then during dual boot it says it can not install grub

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: ubiquity 2.21.63.6 [modified: lib/partman/automatically_partition/question]
ProcVersionSignature: Ubuntu 4.13.0-36.40~16.04.1-generic 4.13.13
Uname: Linux 4.13.0-36-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.15
Architecture: amd64
CasperVersion: 1.376.2
Date: Sat Apr 7 00:09:58 2018
InstallCmdLine: file=/cdrom/preseed/ubuntu.seed boot=casper initrd=/casper/initrd.lz quiet splash --- maybe-ubiquity
LiveMediaBuild: Ubuntu 16.04.4 LTS "Xenial Xerus" - Release amd64 (20180228)
ProcEnviron:
 LANGUAGE=en_IN
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_IN
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)

[Phillip Susi (psusi)]

Your primary boot drive is partitioned with GPT but you are not booting in UEFI mode. This requires you to create a 1 mb bios_grub partition.