Fix Step3 null model exception (#508)
Fix Step3 null model exception (#508)

- Fix null exception when Model is empty on Step3
MCLD/greatreadingadventure,MCLD/greatreadingadventure,MCLD/greatreadingadventure,iafb/gra4,haraldnagel/greatreadingadventure,MCLD/gra4,haraldnagel/gra4,MCLD/greatreadingadventure,haraldnagel/gra4,MCLD/gra4,haraldnagel/greatreadingadventure,haraldnagel/greatreadingadventure,iafb/gra4,haraldnagel/greatreadingadventure,MCLD/greatreadingadventure