No icon for mono-audio devices

Submitted by Will Cooke

Assigned to Alexander Larsson @alexl

Mono audio devices, such as Bluetooth HSP/HDP headsets, don't have a suitable icon.

When using the sound panel in Control Center to test the audio on these types of device the broken-icon icon is shown.

The missing icons are "audio-speaker-mono.svg" and ""audio-speaker-mono-testing.svg".

Version: ALL