修复音量设置问题

lib/video.dart

@@ -248,7 +248,7 @@ class GZVideoPlayerState extends State<GZVideoPlayer>
   @override
   void didChangeMetrics() {
     WidgetsBinding.instance.addPostFrameCallback((timeStamp) {
-      if (!_hasShow) return;
+      if (!mounted || !_hasShow) return;
       var orientation = MediaQuery.of(context).orientation;
       bool fullscreen = false;
       if (orientation == Orientation.landscape) {
@@ -388,7 +388,7 @@ class GZVideoPlayerState extends State<GZVideoPlayer>
       vol = 0.0;
     }
     if (vol >= 1.0) {
-      vol = 0.0;
+      vol = 1.0;
     }
     if (_controller.value.isInitialized) {
       widget.onVolume?.call(vol);