adding default fallback basemap attribute
adding default fallback basemap attribute

dbirchak/cartodb,codeandtheory/cartodb,thorncp/cartodb,dbirchak/cartodb,splashblot/dronedb,future-analytics/cartodb,thorncp/cartodb,CartoDB/cartodb,CartoDB/cartodb,DigitalCoder/cartodb,future-analytics/cartodb,codeandtheory/cartodb,CartoDB/cartodb,UCL-ShippingGroup/cartodb-1,thorncp/cartodb,dbirchak/cartodb,bloomberg/cartodb,bloomberg/cartodb,nyimbi/cartodb,thorncp/cartodb,raquel-ucl/cartodb,CartoDB/cartodb,bloomberg/cartodb,raquel-ucl/cartodb,future-analytics/cartodb,UCL-ShippingGroup/cartodb-1,nuxcode/cartodb,nyimbi/cartodb,DigitalCoder/cartodb,DigitalCoder/cartodb,CartoDB/cartodb,nuxcode/cartodb,thorncp/cartodb,codeandtheory/cartodb,nuxcode/cartodb,nyimbi/cartodb,raquel-ucl/cartodb,codeandtheory/cartodb,future-analytics/cartodb,splashblot/dronedb,raquel-ucl/cartodb,nuxcode/cartodb,UCL-ShippingGroup/cartodb-1,bloomberg/cartodb,bloomberg/cartodb,codeandtheory/cartodb,future-analytics/cartodb,splashblot/dronedb,splashblot/dronedb,nuxcode/cartodb,UCL-ShippingGroup/cartodb-1,dbirchak/cartodb,UCL-ShippingGroup/cartodb-1,nyimbi/cartodb,dbirchak/cartodb,DigitalCoder/cartodb,raquel-ucl/cartodb,DigitalCoder/cartodb,nyimbi/cartodb,splashblot/dronedb