为什么运行代码'FirebaseAuth.getInstance（）。signOut（）;'时我的应用程序崩溃？

Question

//这是导致错误的代码
//最近3小时尝试了此问题，没有任何解决方法

FirebaseAuth.getInstance().signOut();
                                        intent = new Intent(StartActivity.this, LoginActivity.class);
                                        intent.setFlags(Intent.FLAG_ACTIVITY_NEW_TASK | Intent.FLAG_ACTIVITY_CLEAR_TASK);
                                        startActivity(intent);

//我的依赖项

 implementation 'com.google.firebase:firebase-core:16.0.9'
    implementation 'com.google.firebase:firebase-database:17.0.0'
    implementation 'com.google.firebase:firebase-auth:17.0.0'
    implementation 'com.google.android.gms:play-services-auth:16.0.1'
    implementation 'com.firebaseui:firebase-ui-auth:4.0.0'
    implementation "com.google.android.gms:play-services-gcm:16.1.0"
    implementation 'com.google.firebase:firebase-storage:17.0.0'
    implementation 'com.google.firebase:firebase-messaging:18.0.0'
    implementation 'com.firebase:firebase-client-android:2.5.0'