added ground clause to else-less use of case (issue 93)
added ground clause to else-less use of case (issue 93)

aoh/owl-lisp,yuriy-chumak/OL,yuriy-chumak/OL,yuriy-chumak/OL,yuriy-chumak/OL,aisamanra/owl-lisp,aoh/owl-lisp,aisamanra/owl-lisp,aoh/owl-lisp,yuriy-chumak/OL,yuriy-chumak/OL,aisamanra/owl-lisp