fix: don't precompute infill stuff if infill not present
fix: don't precompute infill stuff if infill not present

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