isInstalled方法报错

[suyie001]

bool isInstalled = await Weibo.instance.isInstalled(); 报错信息如下：
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): Failed to handle method call
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): java.lang.NullPointerException: Attempt to invoke interface method 'boolean com.sina.weibo.sdk.openapi.IWBAPI.isWBAppInstalled()' on a null object reference
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at io.github.v7lin.weibo_kit.WeiboKitPlugin.onMethodCall(WeiboKitPlugin.java:167)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at io.flutter.plugin.common.MethodChannel$IncomingMethodCallHandler.onMessage(MethodChannel.java:267)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at io.flutter.embedding.engine.dart.DartMessenger.invokeHandler(DartMessenger.java:292)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at io.flutter.embedding.engine.dart.DartMessenger.lambda$dispatchMessageToQueue$0$io-flutter-embedding-engine-dart-DartMessenger(DartMessenger.java:319)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at io.flutter.embedding.engine.dart.DartMessenger$$ExternalSyntheticLambda0.run(Unknown Source:12)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at android.os.Handler.handleCallback(Handler.java:942)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at android.os.Handler.dispatchMessage(Handler.java:99)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at android.os.Looper.loopOnce(Looper.java:201)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at android.os.Looper.loop(Looper.java:288)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at android.app.ActivityThread.main(ActivityThread.java:8068)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at java.lang.reflect.Method.invoke(Native Method)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:548)
E/MethodChannel#v7lin.github.io/weibo_kit( 7290): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:942)