disappearing rows

TestView.kt

import javafx.collections.FXCollections
import tornadofx.*

class TestView : View("My View") {
    private val persons = FXCollections.observableArrayList<PersonModel>()
    private val sortedFilteredPersons = SortedFilteredList(persons)

    init {
        persons.add(PersonModel(Person("Jane", "Doe")))
        persons.add(PersonModel(Person("Max", "Doe")))
    }

    override val root = vbox {
        textfield {
            promptText = "Filter"
            sortedFilteredPersons.filterWhen(textProperty(), { query, item ->
                item.firstname.value.contains(query, ignoreCase = true) ||
                item.lastname.value.contains(query, ignoreCase = true)
            })
        }

        tableview<PersonModel> {
            sortedFilteredPersons.bindTo(this)

            column("Firstname", PersonModel::firstname)
            column("Lastname", PersonModel::lastname)
        }
    }
}


data class Person(val firstname: String, val lastname: String)

class PersonModel(person: Person) : ViewModel() {
    val firstname = observable(person, Person::firstname)
    val lastname = observable(person, Person::lastname)
}