anchor.diff:            stream: widget.player.volume,
             initialData: AssetsAudioPlayer.defaultVolume,
             builder: (context, snap) {
  -            return widget.builder(context, snap.data);
  +            if (snap.hasData) {
  +              return widget.builder(context, snap.data)!;
  +            } else {
  +              return SizedBox();
  +            }
             },
           );
         case _PlayingBuilderType.currentPosition:
           return StreamBuilder(
             stream: widget.player.currentPosition,
             initialData: Duration.zero,
  -          builder: (context, snap) {
  -            return widget.builder(context, snap.data);
  +            builder: (context, snap) {
  +            if (snap.hasData) {
  +              return widget.builder(context, snap.data)!;
  +            } else {
  +              return SizedBox();
  +            }
             },
           );
         case _PlayingBuilderType.playSpeed:
           return StreamBuilder(
             stream: widget.player.playSpeed,
             initialData: AssetsAudioPlayer.defaultPlaySpeed,
  -          builder: (context, snap) {
  -            return widget.builder(context, snap.data);
  +           builder: (context, snap) {
  +            if (snap.hasData) {
  +              return widget.builder(context, snap.data)!;
  +            } else {
  +              return SizedBox();
  +            }
             },
           );
         case _PlayingBuilderType.forwardRewindSpeed:
           return StreamBuilder(
             stream: widget.player.forwardRewindSpeed,
  -          initialData: null,
  -          builder: (context, snap) {
  -            return widget.builder(context, snap.data);
  +           builder: (context, snap) {
  +            if (snap.hasData) {
  +              return widget.builder(context, snap.data)!;
  +            } else {
  +              return SizedBox();
  +            }
             },
           );
         case _PlayingBuilderType.current:
           return StreamBuilder(
             stream: widget.player.current,
  -          initialData: null,
  -          builder: (context, snap) {
  -            return widget.builder(context, snap.data);
  +          builder: (context, snap) {
  +            if (snap.hasData) {
  +              return widget.builder(context, snap.data)!;
  +            } else {
  +              return SizedBox();
  +            }
             },
           );
         case _PlayingBuilderType.realtimePlayingInfos:
           return StreamBuilder(
             stream: widget.player.realtimePlayingInfos,
  -          initialData: null,
  -          builder: (context, snap) {
  -            return widget.builder(context, snap.data);
  +           builder: (context, snap) {
  +            if (snap.hasData) {
  +              return widget.builder(context, snap.data)!;
  +            } else {
  +              return SizedBox();
  +            }
             },
           );
         case _PlayingBuilderType.playerState:
           return StreamBuilder(
             stream: widget.player.playerState,
             initialData: PlayerState.stop,
  -          builder: (context, snap) {
  -            return widget.builder(context, snap.data);
  +            builder: (context, snap) {
  +            if (snap.hasData) {
  +              return widget.builder(context, snap.data)!;
  +            } else {
  +              return SizedBox();
  +            }
             },
           );
       }
  
positive.code:     }
      return SizedBox();
    }
  }
  
negative.code:           stream: widget.player.loopMode,
            initialData: LoopMode.none,
            builder: (context, snap) {
              if (snap.hasData) {
                return widget.builder(context, snap.data)!;
              } else {
                return SizedBox();
              }
            },
          );
        case _PlayingBuilderType.volume:
  