I have a Quantal liveUSB at hand and booted from it. I ran the grub-install from it and fixed the boot.
Now when I boot the grub version shows as 2.00. When I can boot to Trusty I ran grub-install again in hope of making the grub version current and I hit this error again.
So it appears there's a bug in the current 2.02 beta version.
It happened to me as well.
I have a Quantal liveUSB at hand and booted from it. I ran the grub-install from it and fixed the boot.
Now when I boot the grub version shows as 2.00. When I can boot to Trusty I ran grub-install again in hope of making the grub version current and I hit this error again.
So it appears there's a bug in the current 2.02 beta version.