Fix null reference in difficulty recommender
Fix null reference in difficulty recommender

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