Muting an Audio Group, mutes all the children, although they are not selected. When muting an Audio Group with children, all the children are also muted unintentionally.

To reproduce:
- Open attached project and launch "AudioMixerTest" scene
- Open the window for audio mixer asset "Ambience" and duck it
- Select the audio group "Child 1"
- Hit Play
- Press the "M" button on the "Child 1" audio group
- Observe that audio group "Child 2" is also muted, although the Mute button is not activated

As a user this seems like a weird behaviour. If I want to mute multiple channels, then I can select multiple audio groups in my Mixer Tree and then press the Mute button.