Kotlinx serialization: I got "NoSuchElementException: List is empty. " when Properties.encodeToMap

I got an exception when invoking Properties.encodeToMap
Is it expected behavior?

sample code id below.

    class Data (val prop: String)
    val data: Data? = Data("prop")
    println(Json.encodeToString(data)) // OK
    println(Properties.encodeToMap(data)) // NG
    println(Properties.encodeToMap(data!!)) // OK


Looks like it might be a bug in Serialization. Making data non-nullable fixes the issue.