FIT Query: metricsAreAbsentUnlessRequested fails

Motivation

The test metricsAreAbsentUnlessRequested() is failing due to the performer returning metrics when not requested.

Root Issue

This is due to the SDK's QueryMetaData object initialising its QueryMetrics property at creation (per RFC, as the property is not nullable) and the performer only checking for null. Since the metrics in the response aren't null, the gRPC object is created and is empty.