panic after entering blank line at mountroot prompt

I recently ran my FreeBSD installation in a virtual machine, 
and when I booted on real hardware I'd forgotten to update /etc/fstab. 
I saw the rootmount prompt and tried to clear away the USB probe 
messages by pressing enter. It appears there's a problem with the
mountroot code though because instead of another line, I got a panic: 
"failed to (re-)mount root". Should the mountroot parser be failing if
it doesn't find a valid root to mount on the first line?

-- 
Bruce Cran