This is more of a feature request than a bug. I don't
think Grip should autorip if it can't find cddb info
for the disc.
If autoripping is for people who want to rip disc after
disc with as little user intervention as possible then
ripping a disc with no info is a bad thing. Unless you
check every disc (which makes autoripping fairly
useless) it's possible you could end up with a whole
lot of "noartist" tracks.
The best solution would be to pop up a dialog box
saying no cddb info was found and asking the user if
they want to proceed with ripping and encoding.