On Tue, Apr 9, 2013 at 5:31 AM, Nick Dokos <ndokos@gmail.com> wrote:
> You can turn on formula debugging with C-c { and then you'd
> see that in Pancho's case, the list is ("") i.e. a list containing the
> empty string - a list of length 1. That might qualify as a bug (or not)

This issue is part of some old bugs that I discovered end of 2012. It
seems like my patch from then
http://orgmode.org/w/org-mode.git?p=org-mode.git;a=commitdiff;h=764315
resolved it only partially and I missed the case of a range with only
empty fields, although I tested and approved it in my ERTs... The
attached patch corrects.

It is worth a small compatibility change: For a range with only empty
fields it is now possible and necessary to choose different behaviors
of vmean by adding the format specifiers E and/or N.

Michael