Unfortunately there's no `Muted` property on MPris, so you cannot easily "restore" the previous volume, but that's an issue that affects every player, so when you click mute on a player and then adjust the volume in media controller it raises the volume from 0 rather than just working on the previous volume like the volume plasmoid would
* Clicked mute on a video player, mpris reported zero, and UI reflected muted state by crossing out the volume icon on the player
* Used wheel on media controller to change volume, media player became muted when volume hit 0.0
Shouldn't have any compatibility side-effects since we assume `muted` to be `false` by default so if this field isn't present because mixing older host with newer extension, nothing would change in behavior here.