The original code (rather oddly) interprets a length of zero in

The original code (rather oddly) interprets a length of zero in
subvec() to mean "the whole vector".  Melchior showed a use case
(removal of the first element from a vector) where getting a
zero-length subvector is actually desired.  And since I can't come up
with a good reason for why the "feature" was there in the first place,
out it goes...