"last" vs "sole"

Hi, i'd like to suggest changing the message from

  gdelete: cannot delete the last group

to

  gdelete: cannot delete the sole group

This borrows from the error message visible when
typing `C-x 0' (perhaps twice) in Emacs.

The word "last" implies ordering.  It is ok when you think in the
context of "last in a series of gdelete commands", but not as good
as "sole group" which has no such contextual crutch.

Another idea: "last-remaining".  However, that's inelegant, IMHO.

thi