隐藏键盘报错，但不影响使用，直接运行example也是如此

[weiwill]

版本： cool_ui: ^1.0.0

E/MethodChannel#flutter/textinput(12311): Failed to handle method call
E/MethodChannel#flutter/textinput(12311): java.lang.NullPointerException: Attempt to invoke virtual method 'void io.flutter.plugin.editing.ListenableEditingState.removeEditingStateListener(io.flutter.plugin.editing.ListenableEditingState$EditingStateWatcher)' on a null object reference
E/MethodChannel#flutter/textinput(12311): 	at io.flutter.plugin.editing.TextInputPlugin.clearTextInputClient(TextInputPlugin.java:530)
E/MethodChannel#flutter/textinput(12311): 	at io.flutter.plugin.editing.TextInputPlugin$1.clearClient(TextInputPlugin.java:151)
E/MethodChannel#flutter/textinput(12311): 	at io.flutter.embedding.engine.systemchannels.TextInputChannel$1.onMethodCall(TextInputChannel.java:114)
E/MethodChannel#flutter/textinput(12311): 	at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:233)
E/MethodChannel#flutter/textinput(12311): 	at io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:85)
E/MethodChannel#flutter/textinput(12311): 	at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:818)
E/MethodChannel#flutter/textinput(12311): 	at android.os.MessageQueue.nativePollOnce(Native Method)
E/MethodChannel#flutter/textinput(12311): 	at android.os.MessageQueue.next(MessageQueue.java:386)
E/MethodChannel#flutter/textinput(12311): 	at android.os.Looper.loop(Looper.java:175)
E/MethodChannel#flutter/textinput(12311): 	at android.app.ActivityThread.main(ActivityThread.java:7625)
E/MethodChannel#flutter/textinput(12311): 	at java.lang.reflect.Method.invoke(Native Method)
E/MethodChannel#flutter/textinput(12311): 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524)
E/MethodChannel#flutter/textinput(12311): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987)
E/flutter (12311): [ERROR:flutter/lib/ui/ui_dart_state.cc(186)] Unhandled Exception: PlatformException(error, Attempt to invoke virtual method 'void io.flutter.plugin.editing.ListenableEditingState.removeEditingStateListener(io.flutter.plugin.editing.ListenableEditingState$EditingStateWatcher)' on a null object reference, null, java.lang.NullPointerException: Attempt to invoke virtual method 'void io.flutter.plugin.editing.ListenableEditingState.removeEditingStateListener(io.flutter.plugin.editing.ListenableEditingState$EditingStateWatcher)' on a null object reference
E/flutter (12311): 	at io.flutter.plugin.editing.TextInputPlugin.clearTextInputClient(TextInputPlugin.java:530)
E/flutter (12311): 	at io.flutter.plugin.editing.TextInputPlugin$1.clearClient(TextInputPlugin.java:151)
E/flutter (12311): 	at io.flutter.embedding.engine.systemchannels.TextInputChannel$1.onMethodCall(TextInputChannel.java:114)
E/flutter (12311): 	at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:233)
E/flutter (12311): 	at io.flutter.embedding.engine.dart.DartMessenger.handleMessageFromDart(DartMessenger.java:85)
E/flutter (12311): 	at io.flutter.embedding.engine.FlutterJNI.handlePlatformMessage(FlutterJNI.java:818)
E/flutter (12311): 	at android.os.MessageQueue.nativePollOnce(Native Method)
E/flutter (12311): 	at android.os.MessageQueue.next(MessageQueue.java:386)
E/flutter (12311): 	at android.os.Looper.loop(Looper.java:175)
E/flutter (12311): 	at android.app.ActivityThread.main(ActivityThread.java:7625)
E/flutter (12311): 	at java.lang.reflect.Method.invoke(Native Method)
E/flutter (12311): 	at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:524)
E/flutter (12311): 	at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:987)
E/flutter (12311): )
E/flutter (12311): #0      JSONMethodCodec.decodeEnvelope (package:flutter/src/services/message_codecs.dart:164:7)
E/flutter (12311): #1      MethodChannel._invokeMethod (package:flutter/src/services/platform_channel.dart:158:18)
E/flutter (12311): <asynchronous suspension>
E/flutter (12311): 

[weiwill]

需要隐藏键盘时，调用
FocusScope.of(context).requestFocus(FocusNode());
或
FocusScope.of(context).unfocus();
都会出现上述错误
好像时用这种方式隐藏键盘，会调用openKeyboard()方法

因为需要点击空白，隐藏键盘，所以需要以上面的方式去隐藏键盘

目前使用下面隐藏键盘的方式可以避过这个问题
SystemChannels.textInput.invokeMethod('TextInput.hide');