Fix typerrors in latest version.

- The added WHEN fixes a bug where we would try to run `(insert NIL)`,
which obviously fails.

- The change to the defvar fixes a failing typecheck, somewhere, where a
  `wholenump` was expected.

I just fixed this quickly because these bugs prevented me from updating other packages, when their sources were checked for whitespace errors.  I was hoping you could add the appropriate tests yourself to make sure this stays fixed, as I don't have the time right now.