don't crash with index out of range when removing radios from saved play queue

backend/app.go

@@ -378,7 +378,7 @@ func (a *App) LoadSavedPlayQueue() error {
 	if err := a.PlaybackManager.LoadTracks(queue.Tracks, Replace, false); err != nil {
 		return err
 	}
-	if queue.TrackIndex >= 0 {
+	if queue.TrackIndex >= 0 && queue.TrackIndex < len(queue.Tracks) {
 		// TODO: This isn't ideal but doesn't seem to cause an audible play-for-a-split-second artifact
 		a.PlaybackManager.PlayTrackAt(queue.TrackIndex)
 		a.PlaybackManager.Pause()

backend/savedplayqueue.go

@@ -36,6 +36,13 @@ func SavePlayQueue(serverID string, pm *PlaybackManager, filepath string, server
 			trackIDs = append(trackIDs, item.Metadata().ID)
 		}
 	}
+	if l := len(trackIDs); trackIdx >= l {
+		if l == 0 {
+			trackIdx = 0
+		} else {
+			trackIdx = l - 1
+		}
+	}
 
 	saved := serializedSavedPlayQueue{
 		ServerID:   serverID,