unordf: tweak SPARQL unit test:
unordf: tweak SPARQL unit test:

rasqal 0.9.27 returns no variables for a SPARQL SELECT query with no
results; it is unclear whether that is allowed but it is a corner case
and probably we should not be testing for that.

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core