subtitle.sami: don’t try to decode None
subtitle.sami: don’t try to decode None

fixes: #477

olof/svtplay-dl,olof/svtplay-dl,qnorsten/svtplay-dl,dalgr/svtplay-dl,selepo/svtplay-dl,spaam/svtplay-dl,iwconfig/svtplay-dl,iwconfig/svtplay-dl,qnorsten/svtplay-dl,dalgr/svtplay-dl,selepo/svtplay-dl,spaam/svtplay-dl