avoid creating NSDictionary with nil object
avoid creating NSDictionary with nil object

yunzhongyoulong/MarqueeLabel,suchitabohra/MarqueeLabel,RacZo/MarqueeLabel,ByunghooLim/MarqueeLabel,zmcadam/MarqueeLabel,KBvsMJ/MarqueeLabel,ihello/MarqueeLabel,amitmalhotra/MarqueeLabel,Anish-kumar-dev/MarqueeLabel,cbpowell/MarqueeLabel,litt1e-p/MarqueeLabel,cbpowell/MarqueeLabel