ConvexHull decorater no longer crashes if node has no MeshData
ConvexHull decorater no longer crashes if node has no MeshData

Fixes CURA-2706

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