这是一个带有kotlin的android项目运行时错误

dependencies {
    implementation 'org.jetbrains.kotlin:kotlin-stdlib:1.5.21'
    implementation 'androidx.core:core-ktx:1.6.0'
    // 其他依赖项
}

val str: String? = null
if (str != null) {
    println(str.length)
} else {
    println("String is null")
}

val obj: Any = "Hello, World!"
if (obj is String) {
    println(obj.toUpperCase())
} else {
    println("Not a String")
}

<!-- res/layout/activity_main.xml -->
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Hello, World!" />
</LinearLayout>