What does the direct call do differently from the safe call?

What does the direct call do differently from the safe call?

fun String?.orLabel(): String = this ?: "missing"

fun main() {
    val label: String? = null

    println(label.orLabel())
    println(label?.orLabel())
}

1. missing null
2. missing missing
3. null null
4. The direct call fails because label is nullable.