added empty symbol test
added empty symbol test

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