Cann't Change MleaderStyle ArrowSymbol to default value.

Hello.
I try to change MLeaderStyle's ArrowSymbol to default (_ClosedFilled). but cann't.

(setq obj (vla-item (vla-item (vla-get-dictionaries (vla-get-activedocument (vlax-get-acad-object))) "ACAD_MLEADERSTYLE") "Standard"))

(setq arr (vla-get-ArrowSymbol Obj)) ;result : ""

and
(vlax-put-property obj "ArrowSymbol" "_Dot") ; works
(vlax-put-property obj "ArrowSymbol" "") ; error
(vlax-put-property obj "ArrowSymbol" ".") ; error
(vlax-put-property obj "ArrowSymbol" "_ClosedFilled") ; error

How can I change to that using Visual-lisp.