Maybe this bug is filed against the wrong component (grub2) but then one (or more) of the following possible components is buggy:
1. the Ubuntu installer is/was broken because it did not set the "install_devices" setting before 14.04 (my case, I installed with 13.10 installer)
2 If it was not possible to set this option before 14.04 because we had grub1, then it's a fault in Ubuntu's grub1 -> grub2 migration scripts (14.04 release upgrader)
But it's definately not "invalid". As you can see more and more people are hit by it...
Maybe this bug is filed against the wrong component (grub2) but then one (or more) of the following possible components is buggy:
1. the Ubuntu installer is/was broken because it did not set the "install_devices" setting before 14.04 (my case, I installed with 13.10 installer)
2 If it was not possible to set this option before 14.04 because we had grub1, then it's a fault in Ubuntu's grub1 -> grub2 migration scripts (14.04 release upgrader)
But it's definately not "invalid". As you can see more and more people are hit by it...