fix: optional assignment used wrong constructor (CURA-833)
fix: optional assignment used wrong constructor (CURA-833)

ROBO3D/CuraEngine,totalretribution/CuraEngine,Ultimaker/CuraEngine,totalretribution/CuraEngine,ROBO3D/CuraEngine,totalretribution/CuraEngine,alephobjects/CuraEngine,alephobjects/CuraEngine,alephobjects/CuraEngine,Ultimaker/CuraEngine,ROBO3D/CuraEngine