fix: Missing null check

lib/pages/recording_dialog.dart

@@ -42,10 +42,11 @@ class _RecordingDialogState extends State<RecordingDialog> {
           path: _recordedPath, encoder: AudioEncoder.AAC);
       setState(() => _duration = Duration.zero);
       _recorderSubscription?.cancel();
-      _recorderSubscription = Timer.periodic(Duration(seconds: 1), (_) async {
+      _recorderSubscription =
+          Timer.periodic(Duration(milliseconds: 100), (_) async {
         _amplitude = await _audioRecorder.getAmplitude();
         setState(() {
-          _duration += Duration(seconds: 1);
+          _duration += Duration(milliseconds: 100);
         });
       });
     } catch (e, s) {
@@ -71,8 +72,9 @@ class _RecordingDialogState extends State<RecordingDialog> {
   @override
   Widget build(BuildContext context) {
     const maxDecibalWidth = 64.0;
-    final decibalWidth = ((_amplitude.current / _amplitude.max) * 2) *
-        (maxDecibalWidth / 4).toDouble();
+    final decibalWidth =
+        ((_amplitude == null ? 0 : _amplitude.current / _amplitude.max) * 2) *
+            (maxDecibalWidth / 4).toDouble();
     final time =
         '${_duration.inMinutes.toString().padLeft(2, '0')}:${(_duration.inSeconds % 60).toString().padLeft(2, '0')}';
 
@@ -86,7 +88,7 @@ class _RecordingDialogState extends State<RecordingDialog> {
                   height: maxDecibalWidth,
                   alignment: Alignment.center,
                   child: AnimatedContainer(
-                    duration: Duration(seconds: 1),
+                    duration: Duration(milliseconds: 100),
                     width: decibalWidth,
                     height: decibalWidth,
                     decoration: BoxDecoration(