fix: naive estimates don't assume last extruder plan has points (CURA-3339)
fix: naive estimates don't assume last extruder plan has points (CURA-3339)

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