Fix the strange error message at boot after Debian update from Jessie to Stretch: ‘error: no symbol table’

sudo grub-install /dev/sda # Just change sda by the location of your boot partition /dev/sdX, where X is the drive (letter) on which you want GRUB to write the boot information. Normally users should not include a partition number, which would produce an error message as the command would attempt to write the information to a partition.
sudo update-grub