Improving AMCoreAudio `volumeInfoForChannel(_:, andDirection:)` so it does not return a VolumeInfo struct unless it is actually populated with any valid values.
Improving AMCoreAudio `volumeInfoForChannel(_:, andDirection:)` so it does not return a VolumeInfo struct unless it is actually populated with any valid values.

rnine/AMCoreAudio,rnine/AMCoreAudio,rnine/AMCoreAudio