Skip metric update if no values are defined in configuration

[Arnoways]

With the recent addition of histograms to measure query times, we might have no interest in defining values for our queries. Even with allow_zero_rows set to true, we still end up with errors within the logs. This PR corrects minor typos and adds a condition that will skip the updateMetrics if q.values is empty

[dewey]

Thank you, this looks good!