Hi!

It seems that org-split-string was rewritten, and handles empty strings
differently in org-mode 9.1. Before (org-split-string "" " ") would return
nil, but now it returns '(""). I couldn't see any information in the
changelog about this.

A side effect (among others, I would guess) of this is that
org-entry-get-multivalued-property and org-entry-put-multivalued-property
now return that a property always have a value, even though it is empty.

Emacs  : GNU Emacs 25.2.1 (x86_64-w64-mingw32)
 of 2017-04-24
Package: Org mode version 9.1 (9.1-elpaplus @
c:/home/.emacs.d/elpa/org-plus-contrib-20170906/)