Replace unnecessary empty skin implementation with null
Replace unnecessary empty skin implementation with null

ppy/osu,smoogipoo/osu,peppy/osu,NeoAdonis/osu,NeoAdonis/osu,peppy/osu,NeoAdonis/osu,UselessToucan/osu,smoogipooo/osu,ppy/osu,UselessToucan/osu,UselessToucan/osu,peppy/osu,ppy/osu,peppy/osu-new,smoogipoo/osu,smoogipoo/osu