Fix parsing empty strings

Julien LepillerThu Apr 02 15:27:51+0200 2020

696a4c5

guile-rdf/rdf
namelast commitdate
rdf.scmAdd graph comparisonThu Apr 02 03:19:49+0200 2020
xsd.scmInitial commitTue Mar 31 04:36:06+0200 2020