fix. ios native type cast

ios/RCTAgora/RCTAgora.m

 RCT_EXPORT_METHOD(startAudioMixing:(NSDictionary *) options
                   resolve:(RCTPromiseResolveBlock)resolve
                   reject:(RCTPromiseRejectBlock)reject) {
-  NSInteger res = [self.rtcEngine startAudioMixing:[options[@"filepath"] stringValue]
+  NSInteger res = [self.rtcEngine startAudioMixing:[options[@"filepath"]]
                                           loopback:[options[@"loopback"] boolValue]
                                            replace:[options[@"replace"] boolValue]
                                              cycle:[options[@"cycle"] integerValue]];
                   resolve:(RCTPromiseResolveBlock)resolve
                   reject:(RCTPromiseRejectBlock)reject) {
   NSInteger res = [self.rtcEngine playEffect:(int)[options[@"soundid"] integerValue]
-                                    filePath:[options[@"filepath"] stringValue]
+                                    filePath:[options[@"filepath"]]
                                    loopCount:(int)[options[@"loopcount"] integerValue]
                                        pitch:[options[@"pitch"] doubleValue]
                                          pan:[options[@"pan"] doubleValue]
                   resolve:(RCTPromiseResolveBlock)resolve
                   reject:(RCTPromiseRejectBlock)reject) {
   AgoraAudioRecordingQuality qualityType = (AgoraAudioRecordingQuality)[options[@"quality"] integerValue];
-  NSInteger res = [self.rtcEngine startAudioRecording:[options[@"filepath"] stringValue] quality:qualityType];
+  NSInteger res = [self.rtcEngine startAudioRecording:[options[@"filepath"]] quality:qualityType];
   if (res == 0) {
     resolve(nil);
   } else {