You still can try to fix this interrupted upgrade from a live USB/CD.
To fix from a live USB/CD, boot into the live system then connect to Internet from the live system and open a terminal then follow these steps:
Run:
sudo fdisk -l
And identify your root partition. It could be something like /dev/sda1
then mount it to /mnt
like so:
sudo mount /dev/sda1 /mnt/
Then run:
sudo mount --bind /proc/ /mnt/proc/
Then run:
sudo mount --bind /sys/ /mnt/sys/
Then run:
sudo mount --bind /dev/ /mnt/dev/
Then run:
sudo cp /etc/resolv.conf /mnt/etc/resolv.conf
Then run:
sudo chroot /mnt/
Now you are in your original system on the hard disk. Run first:
dpkg --configure -a
Then, update APT like so:
apt update
Then, install upgrades like so:
apt upgrade
When finished run:
exit
Then run:
sudo umount /mnt/dev/
Then run:
sudo umount /mnt/sys/
Then run:
sudo umount /mnt/proc/
Then run:
sudo umount /mnt/
Then reboot to your original system, it should be fixed