Created attachment 3069 xfce4-mixer-applet-notrack-fix When the mixer applet is not configured with any device or mixer track, the volume button is still usable. For example, scrolling still works and gives the impression the volume does change, while it does not. The attached patch fixes this behaviour. When no device or track is available the volume button shows the muted icon.
Fixed in commit bd01221ec80da339af7cba076d46aa3fdeee4053.