The getter '_nextController' was called on null.

[hrongyong]

I added two Stream at audioplayers.dart，Used to monitor the click event of the ios notification bar。
I wrote according to onPlayerCompletion writing method, but the above problem appeared。

2020-07-21 10:35:00.103918+0800 Runner[1142:420672] [VERBOSE-2:ui_dart_state.cc(157)] Unhandled Exception: NoSuchMethodError: The getter '_nextController' was called on null.
Receiver: null
Tried calling: _nextController
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:53:5)
#1 AudioPlayer._doHandlePlatformCall (package:audioplayers/audioplayers.dart:639:18)
#2 AudioPlayer.platformCallHandler (package:audioplayers/audioplayers.dart:573:7)
#3 MethodChannel._handleAsMethodCall (package:flutter/src/services/platform_channel.dart:409:55)
#4 MethodChannel.setMethodCallHandler. (package:flutter/src/services/platform_channel.dart:377:54)
#5 _DefaultBinaryMessenger.handlePlatformMessage (package:flutter/src/services/binding.dart:199:33)
#6 _invoke3. (dart:ui/hooks.dart:290:15)
#7 _rootRun (dart:async/zone.dart:1184:13)
#8 _CustomZone.run (dart:async/zone.dart:1077:19)
#9 _CustomZone.runGuarded (dart:async/zone.dart:979:7)
#10 _invoke3 (dart:ui/hooks.dart:289:10)
#11 _dispatchPlatformMessage (dart:ui/hooks.dart:164:5)

[hrongyong]

Ok fine。is my problem。I forgot to carry playerId parameter when I sent it back on the ios side