fix ios bug.

ios/Classes/SwiftDubbingLibPlugin.swift

@@ -91,7 +91,8 @@ public class SwiftDubbingLibPlugin: NSObject, FlutterPlugin {
     
     func initAudioSession(){
         do {
-            if (!initFlag) {
+//            if (!initFlag) {
+           if (true) {
                 try AVAudioSession.sharedInstance().setCategory(AVAudioSession.Category.playAndRecord, options: .defaultToSpeaker)
                 try AVAudioSession.sharedInstance().setActive(true)
                 initFlag = true
@@ -145,6 +146,7 @@ extension SwiftDubbingLibPlugin {
                 //AVLinearPCMIsFloatKey : true, //是否使用浮点数采样
             ]
             let url = URL(fileURLWithPath: filePath)
+            
             audioRecorder = try AVAudioRecorder(url: url, settings: settings)
             audioRecorder?.prepareToRecord()
             audioRecorder?.record()