Fix import failure of beatmap sets containing duplicate beatmap difficulties
Fix import failure of beatmap sets containing duplicate beatmap difficulties

peppy/osu,ppy/osu,NeoAdonis/osu,DrabWeb/osu,NeoAdonis/osu,2yangk23/osu,EVAST9919/osu,ZLima12/osu,peppy/osu-new,naoey/osu,smoogipoo/osu,johnneijzen/osu,peppy/osu,smoogipoo/osu,UselessToucan/osu,DrabWeb/osu,ppy/osu,naoey/osu,naoey/osu,DrabWeb/osu,smoogipoo/osu,ZLima12/osu,johnneijzen/osu,NeoAdonis/osu,UselessToucan/osu,2yangk23/osu,EVAST9919/osu,smoogipooo/osu,UselessToucan/osu,peppy/osu,ppy/osu