Fix getting old material diameter
Fix getting old material diameter

This diameter works. I still don't know why the properties/diameter one didn't work, but this is good too since they are now equal.

Contributes to issue CURA-2822.

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