Prevent errors on overquota checking for organizations withoug owner
Prevent errors on overquota checking for organizations withoug owner

Note that the methods of DataServicesMetricsHelper were already
checking for nil owners. For consistency with existing methods,
nil is return in case of lack of owner in all cases.

Fixes #8017

splashblot/dronedb,splashblot/dronedb,splashblot/dronedb,CartoDB/cartodb,CartoDB/cartodb,splashblot/dronedb,CartoDB/cartodb,CartoDB/cartodb,splashblot/dronedb,CartoDB/cartodb