fix: don't use material_print_temperature_layer_0 if it's zero (CURA-1932)
fix: don't use material_print_temperature_layer_0 if it's zero (CURA-1932)

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