When trying to convert None to RGBA, log it and return a usable default
When trying to convert None to RGBA, log it and return a usable default

contributes to #1869

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