mkinitrd deletes current directory contents if it cannot create tmp dir

Hi, just had a rather unfortunate experience whilst attempting to recover a system where mkinitrd destroyed the contents of my /boot dir.

Basically, if mktemp fails (which it did in my case as /tmp didn't exist), then PRFX is nothing, and this:

rm ${PRFX}*

destroys the contents of the current directory. Would be good to avoid this.