Fix incorrect slider assert logic (and improve flow).
Fix incorrect slider assert logic (and improve flow).

Nabile-Rahmani/osu,ppy/osu,Damnae/osu,RedNesto/osu,NeoAdonis/osu,Frontear/osuKyzer,EVAST9919/osu,peppy/osu-new,naoey/osu,2yangk23/osu,smoogipoo/osu,UselessToucan/osu,johnneijzen/osu,ZLima12/osu,EVAST9919/osu,peppy/osu,DrabWeb/osu,theguii/osu,Drezi126/osu,ppy/osu,UselessToucan/osu,peppy/osu,UselessToucan/osu,smoogipooo/osu,NeoAdonis/osu,tacchinotacchi/osu,NeoAdonis/osu,peppy/osu,naoey/osu,DrabWeb/osu,smoogipoo/osu,ZLima12/osu,naoey/osu,2yangk23/osu,johnneijzen/osu,smoogipoo/osu,ppy/osu,NotKyon/lolisu,DrabWeb/osu,nyaamara/osu,osu-RP/osu-RP