Take the picture down when the queue runs out

The clip stayed frozen on screen after the music ended. Advancing the
queue cleaned up the decoder but never unpublished the video track, and a
published track keeps showing its last frame, so an empty queue left the
bot displaying a still. Every other teardown path (stop, skip, leaving
the channel) already dropped it; the natural end of the queue did not.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/core/player.ts

@@ -428,6 +428,9 @@ export class GuildPlayer extends EventEmitter<GuildPlayerEvents> {
   private async advance(skipLoop: boolean): Promise<void> {
     const finished = this.current;
     this.current = null;
+    // The track has to go with the sound: a published video track keeps showing
+    // its last frame, so the clip would hang on screen after the music stopped.
+    this.stopScreenShare();
     this.currentInput?.cleanup();
     this.currentInput = null;
     this.seekOffset = 0;