Fix missing pre-connect error handler

Author: hiroshihorie

lib/src/core/room_preconnect.dart

@@ -26,6 +26,7 @@ extension RoomPreConnect on Room {
     Duration timeout = const Duration(seconds: 10),
     PreConnectOnError? onError,
   }) async {
+    preConnectAudioBuffer.setErrorHandler(onError);
     await preConnectAudioBuffer.startRecording(timeout: timeout);
     try {
       final result = await operation();

lib/src/preconnect/pre_connect_audio_buffer.dart

@@ -53,7 +53,7 @@ class PreConnectAudioBuffer {
   EventChannel? _eventChannel;
   StreamSubscription? _streamSubscription;
 
-  final PreConnectOnError? _onError;
+  PreConnectOnError? _onError;
   final int _requestSampleRate;
   int? _renderedSampleRate;
 
@@ -301,4 +301,9 @@ class PreConnectAudioBuffer {
     logger.info(
         '[Preconnect audio] sent ${(data.length / 1024).toStringAsFixed(1)}KB of audio (${secondsOfAudio.toStringAsFixed(2)} seconds) to ${agents} agent(s)');
   }
+
+  /// Updates the callback invoked when pre-connect audio fails.
+  void setErrorHandler(PreConnectOnError? onError) {
+    _onError = onError;
+  }
 }