sound applet: Fix album-art never reappearing after changing volume.

This was a regression introduced in f2c054e - this.stream is
never defined.

Fixes #13240.

Author: mtwebster

files/usr/share/cinnamon/applets/[email protected]/applet.js

@@ -1299,7 +1299,7 @@ class CinnamonSoundApplet extends Applet.TextIconApplet {
             if (source === "output") {
                 // if we have an active player, but are changing the volume, show the output icon and after three seconds change back to the player icon unless muted
                 this.set_applet_icon_symbolic_name(this._outputIcon);
-                if (this.stream && !this.stream.is_muted) {
+                if (this._output && !this._output.is_muted) {
                     this._iconTimeoutId = Mainloop.timeout_add_seconds(OUTPUT_ICON_SHOW_TIME_SECONDS, () => {
                         this.setIcon();
                     });