Added check to see if a SceneNode has vertices before adding it
Added check to see if a SceneNode has vertices before adding it

CURA-2460

fieldOfView/Cura,hmflash/Cura,Curahelper/Cura,ynotstartups/Wanhao,ynotstartups/Wanhao,fieldOfView/Cura,hmflash/Cura,Curahelper/Cura