bug fix
bug fix

crash when setText:nil

lcddhr/TOMSMorphingLabel,tomknig/TOMSMorphingLabel,Austinate/TOMSMorphingLabel,Austinate/TOMSMorphingLabel,Austinate/TOMSMorphingLabel,msdgwzhy6/TOMSMorphingLabel,tomknig/TOMSMorphingLabel,tomknig/TOMSMorphingLabel,msdgwzhy6/TOMSMorphingLabel,lcddhr/TOMSMorphingLabel,lcddhr/TOMSMorphingLabel,msdgwzhy6/TOMSMorphingLabel