我试图使一个项目与Firebase登录和注册，我现在尝试使注册活动，我在这里附上代码：

import android.content.Intent
import android.support.v7.app.AppCompatActivity
import android.os.Bundle
import android.text.TextUtils
import android.view.View
import android.widget.EditText
import android.widget.ProgressBar
import android.widget.Toast
import com.google.firebase.auth.FirebaseAuth
import com.google.firebase.auth.FirebaseUser
import com.google.firebase.database.DatabaseReference
import com.google.firebase.database.FirebaseDatabase

class RegisterActivity : AppCompatActivity() {

    private lateinit var txtName:EditText
    private lateinit var txtLastName:EditText
    private lateinit var txtEmail:EditText
    private lateinit var txtPassword:EditText
    private lateinit var progressBar:ProgressBar
    private lateinit var dbReference:DatabaseReference
    private lateinit var database:FirebaseDatabase
    private lateinit var auth:FirebaseAuth

    override fun onCreate(savedInstanceState: Bundle?){
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_register)

        txtName=findViewById(R.id.txtName)
        txtLastName=findViewById(R.id.txtLastName)
        txtEmail=findViewById(R.id.txtEmail)
        txtPassword=findViewById(R.id.txtPassword)

        progressBar=findViewById(R.id.progressBar)

        database= FirebaseDatabase.getInstance()
        auth= FirebaseAuth.getInstance()

        dbReference=database.reference.child("Usuarios")

    }

    fun registrarse(view:View){
        createNewAccount()
    }
    fun login(view:View) {
        startActivity(Intent(this,LoginActivity::class.java))
    }
    private fun createNewAccount(){
        val name:String=txtName.text.toString()
        val lastName:String=txtLastName.text.toString()
        val email:String=txtEmail.text.toString()
        val password:String=txtPassword.text.toString()

        if(!TextUtils.isEmpty(name) && !TextUtils.isEmpty(lastName) && !TextUtils.isEmpty(email) && !TextUtils.isEmpty(password)){
            progressBar.visibility=View.VISIBLE

            auth.createUserWithEmailAndPassword(email,password)
                    ?.addOnCompleteListener(this){

                        task ->

                        if(task.isComplete){
                            val user:FirebaseUser?=auth.currentUser
                            verifyEmail(user)

                            val userBD=dbReference.child(user?.uid)

                            userBD.child("Nombre").setValue(name)
                            userBD.child("Apellidos").setValue(lastName)
                            userBD.child("Correo electrónico").setValue(email)
                            action()
                        }

                    }
        }


    }
    private fun verifyEmail(user:FirebaseUser?){
        user?.sendEmailVerification()
                ?.addOnCompleteListener(this){
                    task ->

                    if(task.isComplete){
                        Toast.makeText(this, "Correo de verificación enviado.",Toast.LENGTH_LONG).show()
                    }
                    else{
                        Toast.makeText(this, "Error al enviar el correo de verificación.",Toast.LENGTH_LONG).show()
                    }
                }
    }
    private fun action(){
        startActivity(Intent(this,LoginActivity::class.java))
    }

}

当我按下按钮"registrarse"时，应用程序崩溃...我的Gradle文件（应用程序）如下所示：

apply plugin: 'com.android.application'

apply plugin: 'kotlin-android'

apply plugin: 'kotlin-android-extensions'

android {
    compileSdkVersion 26
    defaultConfig {
        applicationId "com.example.uburr.hastalos"
        minSdkVersion 24
        targetSdkVersion 26
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }
}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation "org.jetbrains.kotlin:kotlin-stdlib-jre7:$kotlin_version"
    implementation 'com.android.support:appcompat-v7:26.1.0'
    implementation 'com.android.support.constraint:constraint-layout:1.0.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.1'
    implementation 'com.google.firebase:firebase-core:12.0.1'
    implementation 'com.google.firebase:firebase-database:12.0.1'
    implementation 'com.google.firebase:firebase-auth:12.0.1'
    implementation 'com.google.firebase:firebase-storage:12.0.1'
    implementation 'com.google.firebase:firebase-messaging:12.0.1'

}
apply plugin: 'com.google.gms.google-services'

编译器没有显示任何错误。我是新来的，所以我真的不知道如何修复这个...我正在努力学习，我想这个论坛会帮助我，我会非常感谢每个人试图帮助。
03 - 30 17：23：03.636 12627 - 12627/com.示例. uburr. hastalos E/安卓系统运行时间：致命异常：主要工艺：com.示例.下. hastalos，PID：12627 java. lang.空指针异常：无法为以下位置的child（）中的参数"pathString"传递空值：com. google. firebase. database.数据库引用. child（未知来源），网址为com. example. uburr. hastalos. RegisterActivity$createNewAccount$1.onComplete（注册活动. kt：69），网址为www.example. com（未知来源），网址为android. os。处理程序. handleCallback（处理程序. java：751），网址为android. os。处理程序. dispatchMessage（处理程序. java：95），网址为android. app。活动线程. main（活动线程. java：6119），网址为java. lang. reflect. Method。调用（本地方法），网址为com. android. internal. os. ZygoteInit $com.google.android.gms.tasks.zzf.run出队缓冲区： www.example.com 退出队列缓冲区失败03 - 30 17：23：14.793 12627 - 12733/com.示例. uburr. hastalos W/OpenGL渲染器：swapBuffers在0x7f6b9f2380上遇到EGL错误12301，正在停止呈现... dequeueBuffer failed 03-30 17:23:14.789 12627-12733/com.example.uburr.hastalos I/Adreno: DequeueBuffer: dequeueBuffer failed 03-30 17:23:14.793 12627-12733/com.example.uburr.hastalos W/OpenGLRenderer: swapBuffers encountered EGL error 12301 on 0x7f6b9f2380, halting rendering...
谢谢你米格尔·安吉尔。